Master of Arts, The Ohio State University, 1913, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2023, Physics

Organic-based materials provide a unique pathway towards low-cost applications and ecologically-friendly alternatives to inorganic and heavy-metal materials currently utilized today. These organic-based materials are comprised mainly of lightweight compounds (e.g. carbon and nitrogen) that are highly abundant and, through modifications of molecular structure or atomic substitution, are highly tunable to produce a substantial variety of material properties. In terms of spintronic, magnonic, and quantum information science and engineering applications, organic-based magnetic materials remain relatively unexplored despite the vast catalog of available materials that have been identified over recent decades. One such magnetic material, vanadium tetracyanoethylene (V[TCNE]x ∼ 2), however, has demonstrated superb low-loss magnetic resonance properties competitive with the yttrium iron garnet (YIG) which has been the gold standard low-loss material for such applications since the 1950's. In contrast to YIG, though, V[TCNE]x boasts unique properties, such as its benign deposition, patterning capabilities, and facile on-chip integration that outperform YIG. However, despite these attractive properties, until recently relatively little is well understood about the electronic, structural, and spin thermal interactions with the magnetic properties of V[TCNE]x. In this thesis, I present recent advancements and explorations into the structural influences and spin-thermal phenomena in V[TCNE]x. First, I cover the structural and optoelectronic properties of V[TCNE]x, responsible for its long-range magnetic ordering. These studies provide a direct theory-experiment understanding of the local structural order where a (ligand) crystal-field splitting is identified suggesting a crystal-field anisotropy contribution in the material. Next, I present studies on the elastic and magnetoelastic properties in V[TCNE]x by statically straining thin films and observing a shift in its ferromag (open full item for complete abstract)

Committee: Ezekiel Johnston-Halperin (Advisor); Jay Gupta (Committee Member); Yuan-Ming Lu (Committee Member); Annika Peter (Committee Member) Subjects: Condensed Matter Physics; Materials Science; Physics

Master of Arts (MA), Bowling Green State University, 2018, Mathematics/Scientific Computation

In this thesis, we study a system of differential equations that are used to model the material deformation due to magnetostriction both theoretically and numerically. The ordinary differential system is a mathematical model for a much more complex physical system established in laboratories. We are able to clarify that the phenomenon of double frequency is more delicate than originally suspected from pure physical considerations. It is shown that except for special cases, genuine double frequency does not arise. In particular, simulation results using the lab data is consistent with the experiment.

Committee: So-Hsiang Chou PhD (Advisor); Kit Chan PhD (Committee Member); Tong Sun PhD (Committee Member) Subjects: Mathematics

Master of Sciences (Engineering), Case Western Reserve University, 2017, Materials Science and Engineering

Advanced power electronic systems, with increased switching frequencies, demand greater efficiency and higher operating temperature inductors. This demand can be met by developing a new magnetic core material. Nanocrystalline magnetic materials, in particular, Fe77Co5.5Ni5.5Zr7B4Cu1, have been developed for use at elevated temperatures. While this nanocrystalline alloy having iron substituted with equal atomic percentages of cobalt and nickel has resulted in small coercivity, 10 A/m, and high Curie temperature, 220°C, magnetostriction persists as the main source of losses. Coercivity in this alloy system has proven to have a strong dependence on the magnetostriction. Through alloy development, low coercivities and high Curie temperatures can be achieved while minimizing magnetostrictive losses. This thesis focuses on varying the magnetic element content in the iron-rich (Fe1-x-yNixCoy)88Zr7B4Cu1 alloy system to minimize magnetostriction. Fe77Ni8.25Co2.75Zr7B4Cu1 has shown the best results with a coercivity of 10 A/m, magnetostrictive coefficient of 4.8 ppm, and Curie temperature of 218°C.

Committee: Matthew Willard Prof. (Advisor); David Matthiesen Prof. (Committee Member); Alp Sehirlioglu Prof. (Committee Member) Subjects: Energy; Engineering; Materials Science; Nanoscience

Master of Science, The Ohio State University, 2012, Mechanical Engineering

Magnetostrictive materials are a class of smart materials that have the capability to convert mechanical energy to magnetic energy and vice versa. This transfer of energy makes these materials good candidates for both sensing and actuation applications. A device constructed of one of these materials could perform the same function as current parts that utilize several components which would increase the durability, and lead to smaller components. The potential uses of these materials cover a broad range of applications, including self-sensing actuators due to the fact that smart materials are bidirectionally-coupled. An additional benefit in relation to sensors is that magnetostrictive materials can operate in a non-contact fashion. Measuring the magnetic response to a stress input can be done using different non-contact techniques which would reduce the complexity from current force sensors. Galfenol, an alloy of iron and gallium, is a promising material for both actuation and sensing due to the moderately large strain it exhibits under a magnetic field combined with the material's mechanical robustness. Galfenol has properties similar to steel which allow for machining, extruding, and other load bearing applications. These mechanical properties make Galfenol unique relative to other smart materials, which generally are brittle. This research looks to further the study of Galfenol by documenting the behavior of Fe81.6Ga18.4 under various loading conditions in relation to the development of a force sensor. The characterization of these alloys involves applying a stress to the sample and measuring the corresponding change in magnetization. Both major and minor loop responses were observed over a range of stresses and fields. These were compared for sensitivity and used to determine model parameters. Additional minor loop testing was conducted at high frequencies to determine the material's dynamic behavior as a sensor. The sensitivity was observed to decrease with in (open full item for complete abstract)

Committee: Marcelo Dapino Dr (Advisor); Xiaodong Sun (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2011, Mechanical Engineering

Magnetostrictive materials deform in response to applied magnetic fields and change their magnetic state when stressed. Because these processes are due to moment realignments, magnetostrictive materials are ideally suited for sensing and actuation mechanisms with a bandwidth of a few kHz. Significant research effort has been focused on two magnetostrictive alloys: Terfenol-D (an alloy of terbium, iron and dysprosium) and Galfenol (an iron gallium alloy), for their ability to produce giant magnetostrictive strains at moderate fields. Terfenol-D has higher energy density and magnetomechanical coupling factor than Galfenol but it is brittle and suffers from poor machinability. Galfenol on the other hand has excellent structural properties. It can be machined, welded, extruded into complex shapes for use in transducers with 3D functionality. Advanced modeling tools are necessary for analyzing magnetostrictive transducers because these materials exhibit nonlinear coupling between the magnetic and mechanical domains. Also, system level electromagnetic coupling is present through Maxwell's equations. This work addresses the development of a unified modeling framework to serve as a design tool for 3D, dynamic magnetostrictive transducers. Maxwell's equations for electromagnetics and Navier's equations for mechanical systems are formulated in weak form and coupled using a generic constitutive law. The overall system is approximated hierarchically; first, piecewise linearization is used to describe quasistatic responses and perform magnetic bias calculations. A linear dynamic solution with piezomagnetic coefficients computed at the bias point describes the system dynamics for moderate inputs. Dynamic responses at large inputs are obtained through an implicit time integration algorithm. The framework simultaneously describes the effect of magneto-structural dynamics, flux leakages, eddy currents, and transducer geometry. Being a fully coupled formulation, it yields system lev (open full item for complete abstract)

Committee: Marcelo Dapino PhD (Advisor); Ahet Kahraman PhD (Committee Member); Junmin Wang PhD (Committee Member); Rajendra Singh PhD (Committee Member) Subjects: Electromagnetics; Electromagnetism; Mechanical Engineering; Mechanics

Master of Science, The Ohio State University, 2009, Mechanical Engineering

Galfenol is a class of smart material that combines moderate magnetostriction (upto 400 ppm) and excellent mechanical strength. In this work two <100> oriented highly textured polycrystalline Galfenol alloys with different Gallium (Ga) content have been characterized. The two alloys have been studied under tensile and compressive loads. Magnetization versus field measurements are presented for the two alloys at different bias stresses ranging from -63.71 MPa to 63.71 MPa. The magnetization versus applied stress measurements are presented for the two alloys at different bias fields. The stress-dependent magnetic susceptibility change of these alloys has been studied; the susceptibility of the higher concentration Ga alloy is more sensitive to stress in the domain rotation region of the magnetization process and operates over a larger stress range, whereas the low Ga concentration sample is more sensitive in the domain wall motion region. The stress-dependent susceptibility change of these alloys can be used to develop a force sensor or a torque sensor. A force sensor which utilizes the principle of stress-dependent susceptibility is demonstrated. The stress range for a force sensor using the two alloys is determined. The same principle can be used to measure the torque in a non-contact way by bonding rolled Galfenol steel on a shaft.The principle is demonstrated by measuring the change in susceptibility that occurs when a rolled Galfenol patch bonded on a non-magnetic substrate is stressed.

Committee: Marcelo Dapino (Advisor); Stephen Bechtel (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2009, Mechanical Engineering

Magnetostrictive materials have the ability to transfer energy between the magnetic and mechanical domains. They deform in response to magnetic fields and magnetize in response to stresses. Further, their stiffness and permeability depend on both magnetic field and stress. Galfenol, an alloy of iron and gallium, is an emerging magnetostrictive material which is unique for its combination of high magnetomechanical coupling and steel-like structural properties. Unique among smart materials, Galfenol can serve both as a structural element and as an actuator or sensor. This work presents nonlinear characterization and modeling of magnetization and strain of Galfenol, and a 3-D system-level model for Galfenol-based transducers. Magnetomechanical measurements are presented which reveal that Galfenol constitutive behavior is kinematically reversible and thermodynamically irreversible. Magnetic hysteresis resulting from thermodynamic irreversibilities is shown to arise from a common mechanism for both magnetic field and stress application. Linear regions in constant-stress magnetization curves are identified as promising for force sensing applications. It is shown that the slope of these linear regions, or the magnetic susceptibility, is highly sensitive to stress. This observation can be used for force sensing; the 19-22 at. % Ga range is identified as a favorable Galfenol composition for sensing, due to its low anisotropy with moderate magnetostriction and saturation magnetization. A thermodynamic framework is constructed to describe the magnetization and strain. An elementary hysteron, derived from the first and second laws, describes the underlying nonlinearities and hysteresis. Minimization of the energy of a single magnetic domain gives expressions for the hysteron states and accurately describes features of the constitutive behavior, including the stress dependence in the magnetization regions and the stress dependence of the location of the burst magnetization regio (open full item for complete abstract)

Committee: Marcelo Dapino PhD (Advisor); Joseph Heremans PhD (Committee Member); Ahmet Kahraman PhD (Committee Member); Menq Chia-Hsiang PhD (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering