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Magnetization and Transport Study of Disordered Weak Itinerant Ferromagnets

Ubaid Kassis, Sara
http://rave.ohiolink.edu/etdc/view?acc_num=kent1247865424

Abstract Details

2009, PHD, Kent State University, College of Arts and Sciences / Department of Physics.
The study of quantum phase transitions (QPT) provides a new route to find and understand unconventional phases in condensed matter physics. The presently studied alloy, Ni(1-x)Vx, offers an opportunity to investigate a ferromagnetic quantum phase transition, a transition from a ferromagnetic ordered state into a paramagnetic state at T = 0 K, by varying the vanadium concentration, x. Magnetization and transport measurements are used to probe the critical behavior of the phase transition and characterize the onset of “unconventional behavior” such as non-Fermi liquid behavior, which signals a deviation from Fermi liquid theory, a fundamental concept in metals. Towards 11.2 % vanadium, the Curie temperature (Tc) is reduced to zero from its pure nickel value of Tc = 627 K. The critical behavior of the phase transition in samples with the higher nickel content (x < 11%) at a finite Tc essentially follows theories as expected for weak itinerant magnets. The samples with more vanadium (x > 11.2%) do not show a conventional ferromagnetic transition or the typical properties of an ordinary paramagnet. Instead, we see evidence for power laws with unusual exponents in the temperature dependence of the magnetization and the resistivity due to an inhomogeneous magnetic moment distribution. We compare our data findings with recent theories addressing a new critical scenario, quantum phase transitions with disorder. One signature is a Quantum Griffiths’ phase which is observed as power laws with non-universal exponents heading towards a T → 0 instability. At very low temperatures, the quantum Griffiths phase in Ni-V leads to the formation of a frozen cluster glass phase. To our knowledge, our compound is the first to experimentally show all signatures of a quantum Griffiths phase in an extended regime, and therefore provides an ideal model system for a disordered itinerant 3-d Heisenberg system.
Almut Schroeder, Dr. (Advisor)
Carmen Almasan, Dr. (Committee Member)
David Allender, Dr. (Committee Member)
Songping Huang, Dr. (Committee Member)
Robert Twieg, Dr. (Committee Member)
129 p.
Physics
Ferromagnet; Nickel; Vanadium; Itinerant; Disorder; Griffiths phase; Cluster glass; Quantum Phase Transitions; Quantum Critical Pointet; Nickel; Vanadium; Itinerant Disorder; Griffiths phase; Cluster glass; Quantum Phase Transitions

Recommended Citations

Citations

  • Ubaid Kassis, S. (2009). Magnetization and Transport Study of Disordered Weak Itinerant Ferromagnets [Doctoral dissertation, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1247865424

    APA Style (7th edition)

  • Ubaid Kassis, Sara. Magnetization and Transport Study of Disordered Weak Itinerant Ferromagnets. 2009. Kent State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1247865424.

    MLA Style (8th edition)

  • Ubaid Kassis, Sara. "Magnetization and Transport Study of Disordered Weak Itinerant Ferromagnets." Doctoral dissertation, Kent State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1247865424

    Chicago Manual of Style (17th edition)

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© 2009, all rights reserved.
This open access ETD is published by Kent State University and OhioLINK.