Mesoscopic noise probe of an inhomogeneous colossal magnetoresistance phase

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2012

Author dc:creator

• Merithew, Robert David

Contributors dc:contributor

• Weissman, Michael B.

• epitaxial single-crystal films

Statement dc:rights

• ©2000 Merithew

Language dc:language

en

Identifier

4340048

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/31256