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Title:Magnetism in strongly correlated electron systems
Author(s):Barzykin, Victor Vadimovich
Doctoral Committee Chair(s):Pines, David
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Physics, Condensed Matter
Abstract:This thesis consists of two parts, in which I consider two very different examples of magnetism in strongly correlated electron systems, the high-T$\sb{c}$ materials and heavy fermions.
In the first part, I study the magnetic properties of the high temperature superconductors, using both microscopic models and phenomenology based on the nuclear magnetic resonance and neutron scattering data. The resulting theory proposes a universal phase diagram of the magnetic behavior of the high temperature superconductors and related non-superconducting materials. While the overdoped materials exhibit nearly antiferromagnetic Fermi liquid behavior, for which the mean field description is appropriate, I show, on the basis of NMR experiments, that scaling develops in the underdoped metallic cuprate superconductors, once the antiferromagnetic correlation length exceeds a certain value, $\xi\sb{cr}\simeq2$. In the scaling regime, the value of the dynamical critical exponent is $z=1$, which is a consequence of spin waves present in the excitation spectrum. I show that the region of scaling on the phase diagram coinsides with the region of the so-called "spin pseudogap" behavior, which has been observed in many experiments.
In the second part I consider the possible origin of small magnetic moment in some heavy fermion compounds. Apart from their heavy carrier mass, UPt$\sb3$ and URu$\sb2$Si$\sb2$ exhibit antiferromagnetic long range order with very small average values of magnetic moment, $\mu\sim0.01\mu\sb{B}$. I propose that such transitions are driven by an order parameter which is more complicated than that used for ordinary antiferromagnetism, and that the small antiferromagnetic moment appears as a second order effect as a result of the Dzyaloshinskii-Moriya-type interaction. In this thesis, I derive the complete symmetry classification of such states. I also propose methods of experimental verification of the symmetry of the order parameter.
Issue Date:1995
Rights Information:Copyright 1995 Barzykin, Victor Vadimovich
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9543526
OCLC Identifier:(UMI)AAI9543526

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