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Title:Mesoscopic noise probe of an inhomogeneous colossal magnetoresistance phase
Author(s):Merithew, Robert David
Doctoral Committee Chair(s):Weissman, Michael B.
Department / Program:Physics
Subject(s):epitaxial single-crystal films
Abstract:Epitaxial single-crystal films of La2; 3Ca1; 3Mn03 exhibit large discrete equilibrium resistance fluctuations in the region of phase space where colossal magnetoresistance effects are strongest. The fluctuators' dependence on magnetic field indicates that the resistance steps represent small regions of material fluctuating between a paramagnetic insulating phase and a ferromagnetic conducting phase. The dependences of Boltzmann factors on field and temperature give the magnetic moment and entropy differences between the states, providing quantitative thermodynamic information about the locally homogeneous CMR phase transition in an otherwise inhomogeneous sample. The size of the discrete resistance fluctuations reveals a very inhomogeneous current density. The temperature dependence of some fluctuators provides evidence for thermodynamic effects which stabilize the mixed phase. A separate experiment on the spin glass CuMnAu investigates the effect of strong local anisotropy on spin glass dynamics. The result demonstrates that altering the symmetry of a spin glass Hamiltonian on the scale of the two-spin interaction has a strong qualitative effect on the low-energy frozen spin glass state space.
Issue Date:2000
Genre:Dissertation / Thesis
Other Identifier(s):4340048
Rights Information:©2000 Merithew
Date Available in IDEALS:2012-05-29

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