Noise as a mesoscopic probe of the colossal magnetoresistance effect

Robert D. Merithew; Akilan Palanisami; Frank M. Hess; Michael B. Weissman

doi:10.1117/12.488908

9 May 2003 Noise as a mesoscopic probe of the colossal magnetoresistance effect

Robert D. Merithew, Akilan Palanisami, Frank M. Hess, Michael B. Weissman

Proceedings Volume 5112, Noise as a Tool for Studying Materials; (2003) https://doi.org/10.1117/12.488908
Event: SPIE's First International Symposium on Fluctuations and Noise, 2003, Santa Fe, New Mexico, United States

Abstract

Epitaxial thin films and bulk crystals of the colossal magnetoresistance (CMR) material La_2/3Ca_1/3MnO₃ (LCMO) exhibit large discrete equilibrium resistance fluctuations in the region of phase space where the magnetoresistance effects are strongest. Strongly inhomogeneous current paths allow us to observe the random telegraph signals of individual mesoscopic regions of material fluctuating between the paramagnetic-semiconductor phase and the ferromagnetic-conductor phase. Temperature and field dependences of the Boltzmann factors of individual fluctuators yield measurements of the magnetic moment and entropy differences between these phases, and of the fluctuator volumes. These measurements provide some of the first quantitative thermodynamic information about the locally-homogeneous CMR phase transition in an otherwise strongly inhomogeneous system. Careful analysis of the field- and temperature-dependences allows us to discriminate between fluctuations across the (first-order) CMR phase boundary and fluctuations of magnetic domain orientation deep in the ferromagnetic state. Similar measurements of the closely-related CMR material La_2/3Sr_1/3MnO₃ (LSMO) show almost no noise associated with the CMR transition, consistent with a second-order phase transition in this material.

Citation Download Citation

Robert D. Merithew, Akilan Palanisami, Frank M. Hess, and Michael B. Weissman "Noise as a mesoscopic probe of the colossal magnetoresistance effect", Proc. SPIE 5112, Noise as a Tool for Studying Materials, (9 May 2003); https://doi.org/10.1117/12.488908

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