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Adur, RohanMagnetic Coupling and Relaxation at Interfaces Measured by Ferromagnetic Resonance Spectroscopy and Force Microscopy
Doctor of Philosophy, The Ohio State University, 2014, Physics
The emergent field of spintronics, which utilizes the spin of the electron rather than the charge for information processing, relies on an understanding of interfaces and surfaces of ferromagnetic thin films. An interface between a ferromagnetic thin film and a neighboring material can be engineered to provide tuneable static and dynamic couplings, which manifest as effective fields on the ferromagnet. Ferromagnetic resonance (FMR) is a powerful spectroscopic technique for studying these effective fields and couplings. In addition, FMR has been used to generate a pure spin current at these interfaces, which allows for the transfer of angular momentum without an accompanying charge current. The technique of magnetic resonance force microscopy (MRFM) has allowed the study of spin dynamics at the nanometer scale and with sensitivity down to single electron spins in paramagnetic materials and it would be illuminating to use this technique to study the spin transport behavior near an interface. MRFM uses the field from a magnetic probe to define a sensitive slice in which the resonance condition is met. The combination of MRFM techniques with FMR spectroscopy has, until recently, been limited to the measurement of global properties of a sample due to strong spin-spin exchange interactions that lead to collective spin wave modes that are defined by the sample and not sensitive to the probe field. Recently, the negative dipole field from a high coercivity probe magnet has been used to strongly perturb the spin wave spectrum of metallic ferromagnetic films, resulting in the localization of precessing magnetization in the `field well' of the probe magnet into discrete modes, analogous to the discrete modes of a particle in a quantum well. The localized nature of these modes enables their use as a local probe of magnetic properties, and this has been utilized in the demonstration of FMR imaging of a ferromagnetic thin film using ferromagnetic resonance force microscopy (FMRFM). In this thesis I shall demonstrate the use of FMR spectroscopy and FMRFM to study static and dynamic couplings in ferromagnetic materials with emphasis on interfaces. First, I introduce the basic concepts of ferromagnetic resonance and spin wave relaxation. Second, I present the results of using conventional FMR spectroscopy to study the tuneable static effective fields in a ferromagnet, which manifest as anisotropy fields that define the energy landscape and equilibrium direction of the magnetization. Third, I explore both dipolar and exchange couplings between magnetizations which are dynamic in nature, and only manifest when the magnetizations are precessing. Fourth, I demonstrate the use of FMRFM to observe the modification of localized modes in a ferromagnetic film engineered with a lateral interface. Fifth, I describe the design of an FMRFM microscope and management of spurious background effects in an FMRFM experiment. Sixth, I measure relaxation from the localized modes in an insulating ferromagnetic film, which reveal a size-dependent damping effect that was unexpected in an insulating system. This suggests that spin transport from the interface of the localized mode can dictate its relaxation, even in the absence of conduction electrons. Finally, I observe a frequency-independent linewidth broadening contribution that also depends on mode size and this may give a measure of the inhomogeneous fields within a ferromagnetic sample.

Committee:

P. Chris Hammel (Advisor); Fengyuan Yang (Committee Member); Mohit Randeria (Committee Member); Richard Furnstahl (Committee Member)

Subjects:

Physics

Keywords:

ferromagnetic resonance; ferromagnetic resonance force microscopy; localized mode; confined mode; magnetic resonance force microscope; intralayer spin pumping

Maschino, Tyler StephenFREQUENCY-SELECTIVE DESIGN OF WIRELESS POWER TRANSFER SYSTEMS FOR CONTROLLED ACCESS APPLICATIONS
Master of Science, Miami University, 2016, Computational Science and Engineering
Wireless power transfer (WPT) has become a common way to charge or power many types of devices, ranging from cell phones to electric toothbrushes. WPT became popular through the introduction of a transmission mode known as strongly coupled magnetic resonance (SCMR). This means of transmission is non-radiative and enables mid-range WPT. Shortly after the development of WPT via SCMR, a group of researchers introduced the concept of resonant repeaters, which allows power to hop from the source to the device. These repeaters are in resonance with the WPT system, which enables them to propagate the power wirelessly with minimal losses to the environment. Resonant repeaters have rekindled the dream of ubiquitous wireless power. Inherent risks come with the realization of such a dream. One of the most prominent risks, which we set out in this thesis to address, is that of accessibility to the WPT system. We propose the incorporation of a controlled access schema within a WPT system to prevent unwarranted use of wireless power. Our thesis discusses the history of electromagnetism, examines the inception of WPT via SCMR, evaluates recent developments in WPT, and further elaborates on the controlled access schema we wish to contribute to the field.

Committee:

Dmitriy Garmatyuk, PhD (Advisor); Mark Scott, PhD (Committee Member); Herbert Jaeger, PhD (Committee Member)

Subjects:

Computer Engineering; Electrical Engineering; Electromagnetics; Electromagnetism; Engineering

Keywords:

wireless power transfer; WPT; resonance; magnetic resonance; electromagnetism; power security; power encryption; wireless power transfer security; wireless power transfer encryption; SCMR; strongly coupled magnetic resonance; power transfer;

MA, DANMagnetic Resonance Fingerprinting
Doctor of Philosophy, Case Western Reserve University, 2015, Biomedical Engineering
Magnetic Resonance (MR) is an exceptionally powerful and versatile measurement technique. The basic structure of an MR experiment has remained nearly constant for almost 50 years. Here we introduce a novel paradigm, Magnetic Resonance Fingerprinting (MRF) that permits the non-invasive quantification of multiple important properties of a material or tissue simultaneously through a new approach to data acquisition and post-processing. MRF provides a new mechanism to quantitatively detect and analyze complex changes that can represent physical alterations of a substance or early indicators of disease. MRF can also be used to specifically identify the presence of a target material or tissue, which will increase the sensitivity, specificity, and speed of an MR study, and potentially lead to new diagnostic testing methodologies. Because of its basis in pattern recognition, MRF inherently suppresses measurement errors and thus can improve accuracy and efficiency compared to previous approaches. By taking the advantage of the extra degrees of freedom of the MRF concept, the MRF-Music sequence is presented as a special form of the MRF to improve the patients’ comfort level during the MR scans while still maintaining a high image quality and scan efficiency.

Committee:

Mark Griswold (Advisor); Nicole Seiberlich (Committee Chair); Vikas Gulani (Committee Member); David Wilson (Committee Member); Jeffrey Duerk (Committee Member); Daniela Calvetti (Committee Member)

Subjects:

Biomedical Engineering

Keywords:

Magnetic Resonance Fingerprinting;T1 quantification;T2 quantification;Magnetic Resonance Imaging;Quantitative Magnetic Resonance Imaging

Sokol, Paul E.A study of the quadrupolar glass phase of D2 via proton NMR.
Doctor of Philosophy, The Ohio State University, 1981, Graduate School

Committee:

Not Provided (Other)

Subjects:

Physics

Keywords:

Nuclear magnetic resonance;Proton magnetic resonance;Nuclear quadrupole resonance

Du, ChunhuiProbing Spin Dynamics and Transport using Ferromagnetic Resonance based Techniques
Doctor of Philosophy, The Ohio State University, 2015, Physics
Generation and manipulation of spin is of central importance in modern physics. This intense interest is driven in part by exciting new phenomena in spintronics such as spin Hall effects and spin transfer torque as well as by the growth in new tools enabling microscopic studies. Ferromagnetic resonance (FMR) is a powerful technique to study macro-scale spin ensembles, and an effective method to generate pure spin currents. Combined with scanning capability, it can be used as a spin sensitive microscopy with nano-scale spatial resolution to bring fresh insights in spintronics and achieve local excitation, manipulation, and detection of spin. In the first part of this thesis, I will briefly introduce the field of spintronics. In the second chapter, I demonstrate the use of FMR spectroscopy to study the static and dynamics properties of novel materials. In the third chapter, I present the FMR spin pumping technique in ferromagnetic material/normal metal bilayer to characterize the spin Hall angles for a series of 3d, 4d, and 5d transition metals with widely varying spin-orbit coupling strengths and demonstrate that both atomic number, Z, and d electron count play important roles in spin Hall physics. Those work studies the spin dynamics and transport across the interface defined by material discontinuity in macro-scale sample. To study nano-scale structures, in the forth and fifth chapters, I describe probing and imaging spin dynamics using spin wave modes confined into microscopic volumes in a ferromagnetic film by the spatially inhomogeneous magnetic field of a scanned micromagnetic tip of a ferromagnetic resonance force microscope (FMRFM). It shows the characteristics of the localized mode can be broadly tuned by appropriate selection of the orientation of the tip moment relative to the applied uniform field. Micromagnetic simulations accurately reproduce our experimental results and allow quantitative understanding of the ferromagnetic resonance force microscopy spectra. These results provide a universal method of generating and understanding the tightly confined localized modes in various measurement geometries and material systems with increased freedom in the choice of tip and material, and paves the way to improved spatial resolution for imaging using localized spin wave modes. At last, I demonstrate a design of room temperature FMR force microscope with both imaging and transport capability to study and image spin dynamics and transport across the interface defined by the magnetic textures with nano-scale resolution. The sixth chapter is a conclusion of the entire dissertation.

Committee:

P. Chris Hammel (Advisor); Fengyuan Yang (Committee Member); Ciriyam Jayaprakash (Committee Member); Samir Mathur (Committee Member)

Subjects:

Materials Science; Physics

Keywords:

Ferromagnetic Resonance; Spintronics; Spin Pumping; Scan Probe Force Microscopy; Ferromagnetic Resonance Force Microscopy; Oxides; YIG

Li, XiyingFEW ELECTRON PARAMAGNETIC RESONANCES DETECTION TECHNIQUES ON THE RUBY SURFACE
Doctor of Philosophy, Case Western Reserve University, 2005, Electrical Engineering
A method based on the highly localized Evanescent Microware Microscopy (EMM) is developed to spatially resolve small number of Electron Paramagnetic Resonance (EPR), also called Electron Spin Resonance (ESR) transitions on the surface of a signal crystal ruby (Al2O3 doped with Cr3+). The EMM probe operates at a resonate frequency of 3.7 GHz, corresponding to a classical S-band EPR, in a precisely controlled biasing electromagnetic field in the range of 100 to 7000 Gauss. To obtain the highest signal to noise ratio in the overwhelming noise background, a magnetic field modulation with amplitude of 2.0 Gauss and frequency of 5.2 kHz has been applied along with a Lock-in Amplifier, which detects weak signals in very narrow band frequency. Three distinct EPR peaks detected at 1300, 2800 and 5510 Gauss, have demonstrated that three unpaired Cr3+ electrons have four distinct energy levels in the presence of an external magnetic field. Real-time EPR signal measurement software has been developed to control the biasing magnetic fields, collect and display the EPR signals in real time. To observe the weak EPR signal, the measurement speed is set at 400 ms per data point with the time constant of the lock-in amplifier set at 30 ms. The current EMM probe with system overall Q factor of 4,500-5,500, is capable of resolving 20,000 spin transitions with spin-spin relaxation time of around 3 Nano seconds. While the minimum number of detectable spin centers for the commercially available EPR instruments is more than ten million without any spatial information for the spin centers. With more spatially confined EMM probe, the minimum detectable spin transition is expected to reach about 2,000 spin transitions or lower. The ultimate goal of this research is to achieve the minimum detectable spin transition of one single electron using micro-fabricated Atomic Force Microscopy (AFM) EMM probes.

Committee:

Massood Tabib-Azar (Advisor)

Keywords:

Electron Paramagnetic Resonance; Electron Spin Resonance; EPR, ESR; Microwave Frequency

Hockaday, William C.The organic geochemistry of charcoal black carbon in the soils of the University of Michigan biological station
Doctor of Philosophy, The Ohio State University, 2006, Chemistry

Biomass burning and fossil fuel combustion have resulted in the global distribution and accumulation of black carbon in soils and sediments. Black carbon is currently produced at an estimated rate of 1014 g per year, but little is known about its environmental fate and reactivity. Most of this black carbon is charcoal formed by forest fires. The original research in this dissertation is divided among two overarching themes involving the organic geochemistry of the charcoal deposited to soils by biomass burning. The first theme is oriented toward understanding the importance of environmental charcoal as a geosorbent for hydrophobic contaminants (PAHs). The sorption capacity of environmental charcoal differs significantly from that of recently deposited or lab-generated chars. The competitive sorption of natural organic matter is implicated as the cause of diminished sorption capacity. New sorption models are proposed to address the prediction of PAH uptake by fire-impacted soils.

The second research theme deals with the environmental fate of charcoal black carbon. Advanced imaging and magnetic resonance techniques were used to compare and contrast the morphology and chemical composition of recently-formed forest fire charcoals to those aged in soil. The colonization of charcoal particles by filamentous microorganisms was an intriguing observation that motivated an investigation of the feasibility of enzymatic charcoal degradation. The lignolytic fungal enzyme, laccase, causes a modest but discernable oxidation and humification of soil charcoal. The spectroscopic analyses also extend to natural waters of a fire-impacted watershed as a potential conduit for the export of charcoal black carbon from soils. Condensed aromatic leachates from the soil charcoal are prevalent in the dissolved organic matter of the soil pore, river, and ground water.

Committee:

Patrick Hatcher (Advisor)

Keywords:

black carbon; fire; carbon cycle; nuclear magnetic resonance spectroscopy; Fourier transform ion cyclotron resonance; mass spectrometry; dissolved organic matterc

LaFountain, Richard AValidation of VO2max Assessment and Magnetic Resonance Cardiac Function Measurements Utilizing an MRI Compatible Treadmill
Master of Science, The Ohio State University, 2014, EDU Physical Activity and Educational Services
Abstract Maximum oxygen consumption (VO2max) is considered the gold standard for assessment of cardiorespiratory fitness. Likewise, MRI is considered the gold standard for quantification of cardiac function; however, the MRI-compatible equipment required to combine these two measures has not been available to date. We utilized a specially designed MRI-compatible treadmill, and modified oxygen uptake equipment to eliminate the ferromagnetic components of the mask and headgear to perform a standard VO2max treadmill test immediately adjacent to a clinical MRI system. We sought to determine if values for a VO2max test performed in an MRI room utilizing MRI-compatible equipment were valid and accurate when compared to those obtained in an exercise lab with typical equipment set up. Ten recreationally trained subjects completed two VO2max tests to volitional fatigue in two different settings; an exercise lab and an MRI room. Oxygen and carbon dioxide were measured continuously using a computerized system. Secondary criteria were assessed to confirm maximal exercise. Resting and peak exercise images of the heart were taken before and after maximal exercise to measure global cardiac function parameters including end systolic volume (ESV), end diastolic volume (EDV), cardiac output (CO) and left ventricular ejection fraction (LVEF). VO2max values were different (P=0.033) between testing locations (47.6±8.11 vs 50.0±10.7). All subjects met or exceeded a RER =1.10 and RPE =17 at peak exercise. iii (35.6 s. ± 3.8 s.) elapsed between the end of exercise and start of imaging. At rest vs immediately following peak stress, CO was (5.1 ± 1.0 vs 16.4 ± 5.6) and LVEF was (65.2 ± 3.3 vs 78.4 ± 4.8). Simultaneous VO2max testing was completed in 7 recreationally trained healthy individuals for comparison of the inter-unit variability in two ParvoMedics TrueOne 2400 systems. Despite the equipment modifications required to measure VO2max in the MRI environment, VO2 measurements correspond to those obtained in the exercise lab. The differences in both separate and simultaneous testing produced <4-6% error, within acceptable criteria according to national certification bodies, manufacturers specifications, and previously published studies. MRI-VO2max combined testing offers potential for advanced investigation of exercise physiology and cardiopulmonary disease.

Committee:

Steven Devor (Advisor); Orlando Simonetti (Advisor)

Subjects:

Kinesiology

Keywords:

VO2max; Cardiac Magnetic Resonance; CMR; Exercise; Treadmill; Magnetic Resonance Imaging; MRI

Sheth, Vipul RavindraA CEST MRI METHOD TO MEASURE pH
Doctor of Philosophy, Case Western Reserve University, 2011, Biomedical Engineering
Tumor pH is an important biomarker in cancer. In the following chapters an approach to measure pH by Chemical Exchange Saturation Transfer (CEST) MRI is described. Chapter 1 presents and introduction to molecular imaging, the importance of tumor pH and existing methods of pH measurement by various imaging modalities. Chapter 2 describes the characterization of a PARACEST MRI contrast agent, Yb-DO3A-oAA, for pH measurement. The pH measurement is independent of concentration and T1sat relaxation times, and covers a wider pH measurement range than alternative methods. A new method for fitting PARACEST spectra is shown. Chapter 3 demonstrates the self calibrating nature of CEST MRI with the contrast agent, Yb-DO3A-oAA-TML-ester, to detect esterase enzyme activity in solution and in cell culture media by generating an enzyme-responsive CEST effect that was compared with a control CEST effect from the same agent. In Chapter 4, a new MRI method was developed to simplify MRI acquisition of CEST spectra. Arrayed CEST-FISP and the parameters of this method were optimized for use with PARACEST agents. The arrayed CEST-FISP pulse program simplifies acquisition setup and subsequent analysis, and has strong potential to increase CEST experimental throughput that will facilitate future discoveries. Chapter 5 translates Yb-DO3A-oAA from in vitro to in vivo use to measure pH in a MDA-MB-231 tumor model and mouse muscle. The pharmacodynamics of Yb-DO3A-oAA are investigated and the fitting algorithm described in Chapter 2 is extended to in vivo tissues.

Committee:

Zheng-Rong Lu, PhD (Committee Chair); Christopher Flask, PhD (Committee Member); Vikas Gulani, MD. PhD (Committee Member); Roger Marchant, PhD (Committee Member); Mark Pagel, PhD (Advisor)

Subjects:

Biomedical Engineering

Keywords:

MRI; CEST; PARACEST; Paramagnetic; Saturation; pH; Magnetic Resonance; Chemical Exchange Saturation Transfer; Magnetic Resonance Imaging; Lanthanide

Teeling-Smith, Richelle MarieSingle Molecule Electron Paramagnetic Resonance and Other Sensing and Imaging Applications with Nitrogen-Vacancy Nanodiamond
Doctor of Philosophy, The Ohio State University, 2015, Physics
Electron paramagnetic resonance (EPR) is an established and powerful tool for studying atomic-scale biomolecular structure and dynamics. Yet it requires a homogeneous sample size of approximately 10^15 spin-labeled biomolecules. In contrast, single molecule measurements provide improved insights into heterogeneous behaviors that can be masked by ensemble measurements and are often essential for illuminating the molecular mechanisms behind the function of a biomolecule. In this dissertation, I report EPR measurements of a single labeled biomolecule demonstrating the merging of these two powerful techniques. We have selectively labeled individual double-stranded DNA molecules with nanodiamonds containing nitrogen-vacancy (NV) centers, and optically detected the paramagnetic resonance of the NV nanodiamond probe. Analysis of the spectrum reveals that the characteristic time scale for reorientation of the labeled molecule relative to the applied magnetic field is slow compared to the spin relaxation time of the nanodiamond probe. This demonstration of EPR spectroscopic determination of the dynamics of an individual labeled biomolecular construct provides the foundation for single molecule magnetic resonance studies of complex biomolecular systems. In addition to this single-molecule EPR study, I report on the use of the NV center in diamond as a probe for in-vivo magnetometry, in-vivo fluorescence imaging and temperature sensing, and a tool for the measure of spin resonances in neighboring systems. The NV center in diamond has proven to be powerful tool for sensing and imaging in various systems, with a broad array of undeveloped or underdeveloped applications. The studies included in this dissertation provide a brief overview of a select few experiments that explore these capabilities.

Committee:

P. Chris Hammel (Advisor); Ezekiel Johnston-Halperin (Committee Member); Michael G. Poirier (Committee Member); Ralf Bundschuh (Committee Member)

Subjects:

Biochemistry; Biophysics; Condensed Matter Physics; Molecular Physics; Nanoscience; Nanotechnology; Optics; Physics; Scientific Imaging

Keywords:

NV diamond; Nitrogen-Vacancy Diamond; EPR; Electron Paramagnetic Resonance; DNA; DNA dynamics; confocal microscopy; single molecule spectroscopy; single-molecule measurements; biophysics; biomolecular dynamics; ODMR; Optically detected magnetic resonance

Page, Michael RoyInteractions between spin transport and dynamics studied using spatially resolved imaging and magnetic resonance
Doctor of Philosophy, The Ohio State University, 2016, Physics
In this dissertation, I explore the interactions that occur between transported spins and magnetization dynamics using spatially resolved imaging and magnetic resonance. The integration of spin transport and dynamics will be a crucial aspect of realizing spintronic devices, which seek to improve upon current charge based electronics. Rather than focusing on the charge degree of freedom as in traditional electronics, spintronics seeks to utilize the properties of the electron spin degree of freedom to revolutionize the fundamental operating principles of data processing and storage devices. Spintronics promises greater functionality and energy efficiency in devices based on electron spin. However, improved understanding and control of the spin degree of freedom is required for spintronics to reach its full potential. The work in this dissertation represents efforts towards addressing these requirements. I discuss my work relating to the development of a custom scanned probe microscope allowing simultaneous spatially resolved imaging while imposing transport in electrically active spintronic devices. Using this microscope, I correlate the switching of magnetic electrodes in a graphene spin valve to the resistance states by directly imaging the electrode magnetization configuration while simultaneously measuring the non-local magnetoresistance. I investigate interactions between a ferromagnet driven into resonance and proximal nitrogen vacancy centers in diamond. Spinwaves generated during the decay of the uniform mode driven to ferromagnetic resonance relax the diamond nitrogen vacancy center spins resulting in a change in the fluorescence intensity. This technique allows the study of transport of angular momentum between two separated spin systems, as well as the possibility for the nanoscale imaging of magnetization dynamics. I demonstrate Heusler alloy ferromagnetic materials as high spin polarization spin injectors for device applications by studying their magnetoresistive output as a function of composition at room and low temperatures. Spin injection efficiency is another important aspect in the performance of spintronic devices, and optimization of spin injection will be of importance in creating realistic devices. Another promising avenue for spin injection relies on the spin Hall effect. I discuss efforts at using the spin Hall effect in platinum to inject spins into an aluminum channel to be detected in another platinum electrode by the inverse spin Hall effect without the need for a ferromagnet, thus reducing complications resulting from the stray field of typical ferromagnetic injectors. I discuss exploration of spin pumping devices based on metallic and insulating ferromagnet/graphene bilayers using ferromagnetic resonance and electrical detection of the inverse spin Hall effect. Spin pumping represents another opportunity to study interactions of spin transport and magnetization dynamics, in this case leveraged for efficient spin injection. Finally, I perform magnetic resonance measurements of thin film iron germanium skyrmionic candidate materials. Skrymions are a candidate for high density and low power magnetic recording. Measuring the dynamics of these materials will be important for a full characterization of their properties. I demonstrate detection of multiple magnetic phases in this material, and show evidence of large internal fields, which may be of interest in stabilizing skrymions in thin films.

Committee:

P. Chris Hammel, Professor (Advisor); Jay Gupta, Professor (Committee Member); Richard Hughes, Professor (Committee Member); Ciriyam Jayaprakash, Professor (Committee Member)

Subjects:

Physics

Keywords:

magnetism; spin transport; magnetization dynamics; nitrogen vacancy centers in diamond; optically detected magnetic resonance; ferromagnetic resonance; Heusler alloy spin valves; graphene spin valves; scanning probe microscopy;

Craig, Edward ClaytonApplication of dispersion versus absorption (DISPA) in Fourier transform nuclear magnetic resonance and Fourier transform ion cyclotron mass spectrometry /
Doctor of Philosophy, The Ohio State University, 1987, Graduate School

Committee:

Not Provided (Other)

Subjects:

Chemistry

Keywords:

Fourier transform spectroscopy;Nuclear magnetic resonance;Ion cyclotron resonance spectrometry;Absorption spectra

Burgess, Richard ElyMagnetic resonance imaging at ultra high field: implications for human neuroimaging
Doctor of Philosophy, The Ohio State University, 2004, Biomedical Engineering
Even before the development of magnetic resonance imaging, scientists and engineers repeatedly predicted that, despite the theoretical potential of high field, physical and engineering challenges would prevent the practical realization of gains in signal to noise. Many of the arguments used to disparage high field MRI can be divided into issues of uniform excitation, image distortion, and patient safety. In the former category lies challenges such as RF penetration limitations, dielectric resonances, coil self-resonance, coil-sample interactions, and RF power requirements, which may prevent uniform B1 can best be studied with numerical modeling techniques. Within the second category are effects such as chemical shift artifact, susceptibility distortions, and contrast convergence that can be well studied through analytic techniques and methodical manipulation of imaging parameters. In the category of safety belong RF power deposition and magnetohydrodynamic effects. In this thesis, issues of static field safety will be exhaustively explored and investigation of image contrast and quality will be undertaken to assess the potential of the 8 Tesla system for human neuroimaging. This thesis will specifically examine the theoretical risk of cardiac arrhythmia from induced currents and demonstrate the negligible cardiac, cognitive, and physiological bioeffects through animal and human studies. The extent of signal to noise ratio enhancement possible at 8 Tesla will be assessed and harnessed to obtain high resolution whole brain images. In the end, experimental results and analysis show that, despite the presence of artifact, high resolution images of the human brain with unique contrast can be safely obtained at 8 Tesla.

Committee:

Pierre-Marie Robitaille (Advisor)

Keywords:

magnetic resonance; magnetic resonance imaging; MRI; high field; 8 tesla; high resolution

Storrs, Judd M.Automatic Real-time Targeting of Single-Voxel Magnetic Resonance Spectroscopy
PhD, University of Cincinnati, 2010, Engineering and Applied Science: Biomedical Engineering

Magnetic resonance spectroscopy (MRS) is a non-invasive and non-destructive in vivo technique available on magnetic resonance imaging (MRI) scanners that is used to measure biochemical profiles from localized regions, or volumes-of-interest (VOIs), inside the body. A confounding factor for interpretation and analysis of MRS is spatial inconsistency in selection of VOIs for data collection, which may obscure biochemical alterations and reduce the statistical power of a study. Because VOI selection is performed manually by the MRI operator, consistency both between sessions and among subjects requires careful protocol design and experienced staff. Inter-subject anatomic variation, imprecise experimental protocols, and inter-operator variation contribute to VOI positioning error.

In this work, automatic targeting of VOIs using a standard anatomic atlas was hypothesized to improve spatial consistency for VOIs, both among subjects and between sessions. Subject anatomy is aligned to a template during acquisition of routine high-resolution 3D anatomic imaging. Alignment is computed parallel to acquisition and completes prior to the end of the scan allowing immediate use of the template coordinate system for the next scan. Once aligned, preselected VOIs are transferred from the template for acquisition. Two real-time alignment techniques are compared. The first performs affine alignment of the subject to the ICBM452 template, and the second rigidly aligns subject anatomy between baseline and followup sessions.

The technique was developed using simulations based on archived data from 79 subjects randomly segregated into training (40 subjects for development) and testing groups (39 subjects for evaluation). The accuracy of real-time spatial normalization was evaluated as disagreement with SPM5-derived nonlinear normalization. Median disagreement within the brain was 1.9 mm (largest: 9.1 mm). For comparison, optimal affine alignment was computed directly from nonlinear SPM5 results and had a median disagreement of 1.7 mm (largest: 7.7 mm). Median inter-session (test-retest) disagreement was 0.4 mm (largest: 1.9 mm) for the ICBM452-based technique and 0.2 mm (largest: 0.7 mm) for the rigid-body technique. Comparable results on training and testing groups indicate good generalization of both techniques beyond the training group.

Automatic and manual prescription of MRS was compared for VOIs in the anterior cingulate gyrus (ACG) and left and right inferior frontal gyri (L-IFG and R-IFG). Automatic ICBM452-based selection of nonoblique VOIs improved inter-subject overlap by +19.6%, +29.6%, and +22.4% (ACG, L-IFG, and R-IFG), and inter-session overlap by +16.2%, +15.7%, and +11.3% compared to manual VOI selections. Automatic ICBM452-based prescription of oblique VOIs provided further improvements for inter-subject overlap (+1.0%, +1.4%, +1.1%) and inter-session overlap (+3.0%, +3.2%, +2.7%). Rigid-body coregistration further improved inter-session overlap compared to ICBM452-based normalization both for nonoblique (+3.0%, +3.2%, +2.7%) and oblique (+0.6%, +0.3%, +0.6%) VOIs. Quantitative comparisons of VOI tissue content demonstrated improved anatomic consistency for automatic prescriptions compared to manually selected VOIs.

The availability of rapid, atlas-consistent inter-subject alignment is expected to simplify experimental protocols while simultaneously improving study-wide consistency. These improvements are expected to increase statistical power for group comparisons, facilitate atlas-based research (including combined fMRI and MRS studies), and support the development of biomarkers.

Committee:

Jing-Huei Lee, PhD (Committee Chair); Wen-Jang Chu, PhD (Committee Member); James Eliassen, PhD (Committee Member); William Ball, MD (Committee Member)

Subjects:

Biomedical Research

Keywords:

automatic prescription;brain mapping;magnetic resonance imaging (MRI);magnetic resonance spectroscopy (MRS);reproducibility;image registration

Chang, HenryMagnetic Resonance Imaging and Spectroscopy in the Evaluation and Management of Acute Coronary Syndrome
Doctor of Philosophy, The Ohio State University, 2015, Biomedical Engineering
An acute coronary syndrome (ACS) is a life-threatening event in the heart which affects over one million Americans each year. Although not currently part of the standard of care for ACS, magnetic resonance imaging (MRI) and spectroscopy (MRS) techniques may be able to improve outcomes in patients with ACS. The majority of ACS cases are classified, using electrocardiogram (ECG), as non-ST segment acute coronary syndrome (NSTE-ACS). Diagnosis, risk assessment, and selection of management strategy can be difficult in this syndrome. A novel large animal model was created for study of NSTE-ACS by combining a partial coronary artery stenosis with ventricular pacing. In this animal model, MRI images of the heart were acquired, as well as oxygen respiration rates in myocardial tissue, troponin levels, and histology samples. T2 MRI, a technique which identifies myocardial regions with altered chemistry, was found to be elevated in ischemic myocardium. These T2 changes corresponded to reduced myocardial tissue respiratory function. Reperfusion reversed both T2 elevation and tissue respiratory depression, indicating that the early myocardial changes causing acute T2 elevation are reversible. This important property of T2 was supported by ultrastructural findings indicating myocardial viability and by the lack of late gadolinium enhancement (LGE) positivity or high troponins, which are tests to identify the presence of necrosed myocardium. An elevated T2 value thus may be a highly informative marker of acute reversible myocardial injury in NSTE-ACS and may reflect cellular changes (including respiratory function) which are not detectable by other tests or modalities yet have important implications on clinical decisions for patient management. Reversibly injured myocardium (identified by elevated T2) represents a target for reperfusion strategies that can prevent the progression to myocyte death and restore normal myocardial functionality. After an ACS, all patients are highly recommended to participate in a cardiac rehabilitation / secondary prevention (CR/SP) program, which has been shown to improve outcome metrics in patients such as mortality, quality of life, exercise capacity, and glucose control. However, some cellular properties like mitochondrial function and intramuscular fat, while important to patient health, are difficult to measure and so are not included as part of CR/SP evaluation of patients. Optimized techniques to non-invasively measure in vivo mitochondrial function, using 31P MRS, and intramuscular fat, using 1H MRS, were tested for reproducibility in volunteers. Once a suitable protocol was validated, measurements in ACS patients at the beginning of their CR/SP program were taken. This protocol was found to be reliably performed in a timely manner in any post-ACS patient who does not have MRI contraindications. Changes in mitochondrial function and intramuscular fat due to CR/SP interventions (such as modifications to exercise and diet habits) can be quantified using this protocol and used to evaluate the effectiveness of the CR/SP program. CR/SP supervisors thus may be able to tailor specific programs and activities to optimize the benefits to mitochondrial function and intramuscular fat and improve patient outcomes.

Committee:

Subha Raman, MD (Advisor); Orlando Simonetti, PhD (Committee Member); Elliott Crouser, MD (Committee Member); Stephen Lee, PhD (Committee Member)

Subjects:

Biomedical Engineering; Biomedical Research; Medical Imaging; Medicine

Keywords:

acute coronary syndrome; magnetic resonance imaging; magnetic resonance spectroscopy; animal model; phosphocreatine; t2 mapping

Deshmane, Anagha VishwasPartial Volume Quantification Using Magnetic Resonance Fingerprinting
Doctor of Philosophy, Case Western Reserve University, 2017, Biomedical Engineering
Magnetic resonance imaging (MRI) is a key clinical tool which allows for imaging of biological tissues with large field-of-view, millimeter resolution, and good soft tissue contrast, without exposing the patient to ionizing radiation. Magnetic Resonance Fingerprinting (MRF) is a quantitative MRI method which pairs pseudorandom magnetization excitations and fast image acquisition with dictionary-based reconstruction for simultaneous mapping of multiple tissue and experimental properties, including T1, T2, and off-resonance, from a single experiment performed within a clinically feasible scan time. MRF signal evolutions vary in shape for different combinations of encoded properties. Like other quantitative MRI methods, MRF maps yield quantitative maps in which properties are averaged over the voxel dimensions. However, in the presence of partial volumes, voxel-averaged properties are insufficient to quantitatively assess tissue characteristics such as the potential presence of pathology. It is therefore necessary to quantify both tissue properties and voxel composition. The uniqueness of signal evolutions emanating from different tissue types in MRF allows for both tissue property mapping as well as quantification of partial volumes from the same measurement. In this dissertation, two approaches to partial volume quantification by MR Fingerprinting (PV-MRF) are quantitatively assessed for accuracy in the presence of artifacts and model errors. Applications of PV-MRF are also explored, including segmentation of pathology, improved synthetic imaging, and absolute quantification of sub-voxel tissue species.

Committee:

Mark Griswold (Advisor); Nicole Seiberlich (Committee Chair); Xin Yu (Committee Member); Erkki Somersalo (Committee Member)

Subjects:

Biomedical Engineering; Engineering; Medical Imaging; Radiology

Keywords:

magnetic resonance imaging; quantitative imaging; partial volume; absolute quantification; proton density mapping; subvoxel analysis; tissue characterization; tissue quantification; magnetic resonance fingerprinting;

Kim, JongjooLocalized Ferromagnetic Resonance using Magnetic Resonance Force Microscopy
Doctor of Philosophy, The Ohio State University, 2008, Physics

Magnetic Resonance Force Microscopy (MRFM) is a novel approach to scanned probe imaging, combining the advantages of Magnetic Resonance Imaging (MRI) with Scanning Probe Microscopy.

It has extremely high sensitivity that has demonstrated detection of individual electron spins and small numbers of nuclear spins.

Here we describe our MRFM experiments on Ferromagnetic thin film structures. Unlike ESR and NMR, Ferromagnetic Resonance (FMR) is defined not only by local probe field and the sample structures, but also by strong spin-spin dipole and exchange interactions in the sample. Thus, imaging and spatially localized study using FMR requires an entirely new approach.

In MRFM, a probe magnet is used to detect the force response from the sample magnetization and it provides local magnetic field gradient that enables mapping of spatial location into resonance field. The probe field influences on the FMR modes in a sample, thus enabling local measurements of properties of ferromagnets.

When sufficiently intense, the inhomogeneous probe field defines the region in which FMR modes are stable, thus producing localized modes. This feature enables FMRFM to be important tool for the local study of continuous Ferromagnetic samples and structures.

In our experiments, we explore the properties of the FMR signal as the strength of the local probe field evolves from the weak to strong perturbation limit. This underlies the important new capability of Ferromagnetic resonance imaging, a powerful new approach to imaging ferromagnet. The new developed FMR imaging technique enables FMR imaging and localized FMR spectroscopy to combine spectroscopy and lateral information of ferromagnetic resonance images.

Our theoretical approach agrees well with spatially localized spectroscopy and imaging results. This approach also allows analysis and reconstruction of FMR modes in a sample.

Finally we consider the effect of strong probe fields on FMR modes. In this regime the probe field significantly modifies the FMR modes. In particular we observe the complete local suppression of the FMR mode under the probe. This provides as a new tool for local study of continuous ferromagnetic thin films and microstructures.

Committee:

Peter Christopher Hammel (Advisor)

Subjects:

Physics

Keywords:

Magnetic resonance force microscopy;MRFM;Ferromagnetic resonance; FMR;Ferromagnet;Localized FMR;Spin

Ojha, NavdeepImaging of tissue injury-repair addressing the significance of oxygen and its derivatives
Doctor of Philosophy, The Ohio State University, 2007, Biomedical Engineering
The purpose of this work was to study tissue injury-repair using non-invasive biomedical imaging techniques. We employed Magnetic Resonance Imaging (MRI) to evaluate the effect of focal ischemic insult to brain and heart in rodent models. Electron Paramagnetic Resonance (EPR) Spectroscopy was used to study dermal wound healing in mouse models of excisional wounds. A robust Middle Cerebral Artery Occlusion model of focal cerebral ischemia in rodents was established. Serial evaluation of ischemic damage showed that MRI characteristics of ischemic regions change dynamically in the reperfusion period. It was concluded that prevention of vasogenic edema after ischemia is a valuable therapeutic target, and treatment efficacy may be evaluated with MRI. To assess the redox environment of dermal wound site in vivo, a novel EPR based approach was standardized. Non-invasive measurements of metabolism of topically applied nitroxide 15N-perdeuterated tempone in murine excisional dermal wounds demonstrated that the wound site is rich in oxidants, the level of which peaked two day post-wounding in the inflammatory phase. Using Rac2-deficient mice it was concluded that rac2 significantly contributes to oxidant production at the wound site supporting the healing process. High resolution (11.7T) cardiac MRI and histological approaches were employed in tandem to characterize the progressive secondary damage suffered by the murine myocardium following the initial insult caused by ischemia-reperfusion (IR). IR induced changes in the myocardium were examined at specific time-points post reperfusion. A progressive loss of myocardial function associated with increased infarct volume and worsened regional wall motion was observed both with MRI and histological approaches. It was established that myocardial remodeling following IR included progressive myocardial tissue damage which was tightly associated with loss of cardiac function. The final objective of this dissertation was to test the functional significance of tissue remodeling process induced by hyperoxic shock in the heart in a mouse IR model. Worst cardiac function post IR was observed in animals that suffered highest hyperoxic shock, and lowest loss of function in animals with least shock. The p21 pathway was implicated as a major player in the induction of perceived hyperoxic shock and its functional effects.

Committee:

Chandan Sen (Advisor)

Keywords:

Biomedical Imaging; Magnetic Resonance Imaging; Electron Paramagnetic Resonance; Stroke; Cardiac Remodeling; Wound healing

Jiang, YunDEVELOPMENT OF NOVEL PULSE SEQUENCES FOR MAGNETIC RESONANCE FINGERPRINTING
Doctor of Philosophy, Case Western Reserve University, 2017, Biomedical Engineering
Quantification of tissue properties has long been a research goal in Magnetic Resonance Imaging (MRI). However, the long acquisition time of the conventional quantitative method prohibited its adoption in the clinic. The recently proposed Magnetic Resonance Fingerprinting (MRF) is a novel framework that simultaneously quantifies multiple tissue properties using pseudorandom acquisition parameters. It breaks the convention of MRI which acquires a steady- state signal with fixed acquisition parameters, and thus MRF can exploit all degrees of freedom in the pulse sequence design. With nearly unlimited choices of sequence parameters, the thesis explored and presented MRF methods based on the QUick Echo Split NMR technique (QUEST) to reduce the Specific Absorption Rate (SAR), the Fast Imaging with Steady-state Precession (FISP) to improve the performance with off-resonance, the Double Echo Steady-state (DESS) to quantify diffusion, and a Simultaneous MultiSlice (SMS) MRF to further reduce the acquisition time. The development of these novel methods improves the robustness of MRF and have the potential to extend MRF to wide ranges of applications.

Committee:

Mark Griswold, PhD (Advisor); Nicole Seiberlich, PhD (Committee Chair); Xin Yu, PhD (Committee Member); Erkki Somersalo, PhD (Committee Member); Jeffrey Sunshine, MD,PhD (Committee Member)

Subjects:

Biomedical Engineering

Keywords:

Magnetic Resonance Imaging; Magnetic Resonance Fingerprinting;T1;T2;relaxation;MRI;MRF

Fong, Kin ChungHigh Sensitivity Electron Spin Resonance by Magnetic Resonance Force Microscopy at Low Temperature
Doctor of Philosophy, The Ohio State University, 2008, Physics

This dissertation describes the development and usage of the experimental technique -- Magnetic Resonance Force Microscopy (MRFM) -- to study electron spin resonance at low temperature in sensitivity as high as two electron spins. MRFM detects magnetic resonance by sensing the small force acting on the cantilever by the paramagnetic electron spins in the sample through magnetic coupling. I have applied this technique to measure the fluctuating magnetic moments of few electron spin ensembles known as the statistical polarization or the spin noise.

In this dissertation, I describe the basic principles and setup of the MRFM experiments. I have used the MRFM experiment to verify that applying negative feedback to the cantilever can reduce the cantilever response time without sacrificing the signal-to-noise ratio in the force detection. Using the new spin manipulation scheme and the microwave resonator I designed for low temperature MRFM experiments, MRFM force spectra are measured and understood by modeling the spins undergoing magnetic resonance in an inhomogeneous magnetic field.

I have used the high sensitivity MRFM experiment to observe the real-time fluctuation of the electron spin magnetic moments. From the statistics of this fluctuation, the number of resonating spins and the correlation time of the statistical polarization are measured. I have shown that the spin correlation time is due to the one and two phonon relaxation processes in the silicon dioxide sample by measuring the spin correlation time in various sample temperature. As the fluctuating time scale of the statistical polarization is not dominated by the MRFM instrumentation processes, the measured spin correlation time can be used to enhance image contrast by the relaxation-weighted imaging.

Committee:

P. Christopher Hammel (Advisor); Thomas J. Gramila (Committee Member); Gregory P. Lafyatis (Committee Member); John W. Wilkins (Committee Member)

Subjects:

Physics

Keywords:

Magnetic Resonance Force Microscopy; Magnetic Resonance; Force Detection; High Sensitivity; Cantilever; Spin Correlation Time; Statistical Polarization; Signal Energy; Spin Noise; Low Temperature; Cantilever; Microwave resonator; silica

Lee, Kai MonSolution structures of yeast ribosomal 5S and 5.8S ribonucleic acids via 500 MHz proton nuclear magnetic resonance spectroscopy /
Doctor of Philosophy, The Ohio State University, 1986, Graduate School

Committee:

Not Provided (Other)

Subjects:

Chemistry

Keywords:

Ribosomes;Yeast;RNA;Proton magnetic resonance;Nuclear magnetic resonance spectroscopy

Liu, YuchiDEVELOPMENT OF DYNAMIC PHOSPHORUS-31 AND OXYGEN-17 MAGNETIC RESONANCE SPECTROSCOPY AND IMAGING TECNIQUES FOR PRECLINICAL ASSESSMENT OF ENERGY METABOLISM IN VIVO
Doctor of Philosophy, Case Western Reserve University, 2018, Biomedical Engineering
Adenosine triphosphate (ATP) is the energy currency that maintains physiological activities of the cell. The major source of ATP in aerobic organisms is oxidative phosphorylation occurred in mitochondria. Disruptions of oxidative phosphorylation are associated with various metabolic diseases. Hetero-nuclei MRI plays an important role in assessing functional cell processes such as oxidative metabolism. Specifically, phosphorous-31 (31P) and oxygen-17 (17O) MRS/MRI provide a non-invasive tool to probe mitochondrial oxidative capacity and oxygen consumption, respectively. However, hetero-nuclei MRI in general is challenging due to the low in vivo concentrations and low MR sensitivity. Long acquisition time is usually required even with low spatial resolution. In this thesis, novel approaches for imaging 31P and 17O with high spatial resolution and temporal resolution were developed and demonstrated in small animals at high fields. In particular, this thesis focused on fast 31P MR Spectroscopic Imaging (MRSI) and 17O MRI approaches with non-Cartesian encoding schemes that assess mitochondrial function in skeletal muscle and cerebral oxygen metabolism/water movement across the blood-brain barrier (BBB), respectively. 15 Four projects are described in this thesis. First, an ischemia-reperfusion protocol was established to evaluate mitochondrial oxidative capacity in type 2 diabetic rats using 31P MRS. Second, a fast dynamic 31P MRSI method using a low-rank model was developed and demonstrated in rat skeletal muscle during ischemia-reperfusion. Third, a dynamic 17O MRI method using golden-angle radial acquisition combined with k-space weighted image contrast (KWIC) reconstruction was developed and validated in simulation studies and phantom experiments. Finally, the 17O MRI method was demonstrated in a mouse model with glioblastoma (GBM) to assess the water movement across BBB after a bolus in injection of 17O-labeled water. The 17O MRI approach was also applied to a mouse model of middle cerebral artery occlusion (MCAO) in 17O-labeled gas inhalation experiments to assess cerebral oxygen metabolism in vivo. The success of these studies will pave the way for fast metabolic imaging using 31P and 17O MRI techniques and allow for the assessment of metabolic alterations in various disease models, such as diabetes, ischemic stroke, etc.

Committee:

Xin Yu, Sc.D. (Advisor); Nicole Seiberlich, Ph.D. (Committee Chair); Mark Griswold, Ph.D. (Committee Member); John Kirwan, Ph.D. (Committee Member); Nicola Lai, Ph.D. (Committee Member)

Subjects:

Biomedical Engineering

Keywords:

magnetic resonance imaging, magnetic resonance spectroscopy, energy metabolism, phosphorus-31, oxygen-17

See, Erich MichaelModeling Plasmon Resonance for a Gold Nanoparticle Plasmon-Enhanced Cadmium Sulfide Biosensor
Master of Science, Miami University, 2009, Physics
This paper reports on our research into developing an SPR-enhanced cadmium sulfide (CdS) nanosheet biosensor. Our research centered around two separate tasks. First, we tested various methods of uniformly distributing a specific density of gold nanoparticles onto a CdS nanosheet. Second, we ran a multitude of simulations to identify the resonant wavelength of various gold nanoparticles, as well as determine how strongly the generated electric field penetrated the CdS NS. Through these tests, we determined that the PLL method allowed us to deposit nanoparticles onto the CdS sheet, and our simulations outlined which gold nanoparticle shapes would yield the best results when combined with the CdS sheet. Further studies also included the simulations of gold nanoparticles coated in streptavidin.

Committee:

Jan Yarrison-Rice, PhD (Advisor); Perry Rice, PhD (Committee Member); Khalid Eid, PhD (Committee Member)

Subjects:

Physics

Keywords:

SPR; Surface Plasmon Resonance; Biosensor; streptavidin; Plasmon Resonance

Stockert, Amy L.Spectroscopic and kinetic studies of bovine xanthine oxidase and Rhodobacter capsulatus xanthine dehydrogenase
Doctor of Philosophy, The Ohio State University, 2004, Ohio State Biochemistry Program
Xanthine oxidase (XO) and dehydrogenase (XDH) are molybdenum enzymes that catalyze the conversion of hypoxanthine to xanthine and xanthine to uric acid. The enzymes contain two 2Fe/2S centers, a FAD and a molybdopterin. Research has indicated similar structure and mechanism, thus study of both enzymes prove useful in understanding mechanism. Resonance Raman (rR) studies of reduced enzyme in complex with violapterin (a true catalytic intermediate) allow enzymatic mechanism to be inferred by comparison of calculated shifts to observed shifts. The proposed mechanism utilizes a two-electron reduction from Mo (VI) to Mo (IV) in one step, however, two one-electron steps have also been proposed. To test this alternate mechanism, the one-electron reduction potentials of several substrates were determined and compared to kinetic parameters for each of these substrates. No correlation is observed between these two parameters ruling out the one-electron mechanism. Recombinant wild-type and several variants of RcXDH were used to study residues involved in catalysis. Kinetics for the E232A mutant show slower reaction rates for both the xanthine and hydroxyl-methylpurine (HMP). EPR studies of this mutant with HMP give a signal similar to the very rapid signal seen with the bovine XO with small modifications and remain unchanged in D2O. Kinetic studies on E730 mutants indicate substantial rate decreases as this residue is proposed to act as the active site base initiating catalysis. Wild-type EPR experiments with HMP have also been performed and a signal such as the rapid type I seen with the bovine XO is observed. The signal indicates two inequivalent protons that disappear upon reacting in D2O. In conclusion, resonance Raman studies have supported the computational model of the enzyme-reduced product complex predicted based on our proposed mechanism. Examination of the first step in the reductive half-reaction indicates a single two-electron reduction. Mutational studies of the active site residues of XDH identify E730 as an essential residue, possibly acting as the active site base initiating catalysis.

Committee:

Russ Hille (Advisor)

Keywords:

xanthine oxidase; xanthine dehydrogenase; kinetics; resonance Raman; enzyme mechanism

Lee, InheeNanoscale Ferromagnetic Resonance Imaging using Magnetic Resonance Force Microscopy
Doctor of Philosophy, The Ohio State University, 2010, Physics
Nanoscale patterned magnetic structures and multi-component magnetic devices have been studied actively for applications of highly efficient data storage and non-volatile magnetic memory devices. Those studies demand high resolution magnetic imaging tools which can characterize complex, often buried nanoscale structures. Ferromagnetic Resonance (FMR) is a powerful spectroscopic tool which provides the magnetic characterizing parameters of spectroscopically identified magnetic materials with high precision. However, FMR studies of nanoscale samples are limited due to insufficient sensitivity and lack of imaging capabilities. Scanned probe FMR using Magnetic Resonance Force Microscopy (MRFM) is an excellent tool for understanding nanoscale ferromagnetic structures based on its high sensitivity and high resolution. Non-interacting electron and nuclear spins in MRFM can be excited selectively in the thin sensitive slice defined by the high magnetic field gradient of the magnetic probe tip. The sensitive slice as a probe enables high resolution three-dimensional imaging. However, for ferromagnets, the mechanism for magnetic resonance imaging is quite different due to the strong spin-spin interactions which lead to collective spin wave excitation. Our recent studies of Ferromagnetic Resonance Force Microscopy (FMRFM) have shown that the magnetic probe tip not only detects the FMRFM force, but also perturbs FMR modes, and even distorts or spatially localizes FMR modes using the strongly inhomogeneous probe field. This strong perturbation of probe field enables us to achieve and image quantitative magnetic information in the local region of ferromagnetic structures. In this thesis I will present various FMRFM imaging techniques using the strong inhomogeneous magnetic field of the micromagnetic probe tip. First, FMRFM imaging in a weak probe field will be discussed. In this case, the shapes of magnetostatic modes in FMR are determined by a confined sample structure while the effect of probe field is ignorable. However, FMR peak positions are shifted by the probe field, which allows encoding of the spatial mode profile of magnetostatic modes into FMR resonance field. On the other hand, in a strong probe field, the shapes of FMR modes can be distorted or spatially localized. In particular, localized modes are suitable for FMRFM imaging which provides a map of intrinsic magnetic properties existing within the local area of the sample. Concerning these localized modes, I will present our recent observations, quantitative analysis and their application for FMR imaging with high field sensitivity of the internal field in a ferromagnetic film . Furthermore, I will discuss other quantitative local magnetic characterization methods such as magnetic force microscopy (MFM) induced by a strong inhomogeneous probe tip field and suppressed or distorted FMR modes FMRFM.

Committee:

Chris Hammel (Advisor); Jay Gupta (Committee Member); David Stroud (Committee Member); Louis DiMauro (Committee Member)

Subjects:

Physics

Keywords:

FMR; MRFM; FMRFM; magnetic resonance; imaging; probe field; localized modes

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