Concepedia

Colossal Effects in Transition Metal Oxides Caused by Intrinsic Inhomogeneities

Jan Burgy, Matthias Mayr, V. Martı́n-Mayor, Adriana Moreo, Elbio Dagotto

Physical Review Letters · 2001 · 433 citations · 24 references

Open access

TL;DR

The study draws an analogy to the Griffiths temperature for systems with two competing orders, suggesting that such inhomogeneities can produce a strong susceptibility to external fields, a behavior also seen in underdoped cuprates. The authors investigate how quenched disorder affects the competition between ordered states across a first‑order transition. They introduce a characteristic temperature scale, $T^{*}$, that governs the formation of ordered clusters. Classical models yield a phase diagram with quantum‑critical‑like features, revealing a low‑temperature paramagnetic regime of randomly oriented coexisting clusters that, when applied to manganites, explains colossal magnetoresistance.

Abstract

The influence of quenched disorder on the competition between ordered states separated by a first-order transition is investigated. A phase diagram with features resembling quantum-critical behavior is observed, even using classical models. The low-temperature paramagnetic regime consists of coexisting ordered clusters, with randomly oriented order parameters. Extended to manganites, this state is argued to have a colossal magnetoresistance effect. A scale ${T}^{*}$ for cluster formation is discussed. This is the analog of the Griffiths temperature, but for the case of two competing orders, producing a strong susceptibility to external fields. Cuprates may have similar features, compatible with the large proximity effect of the very underdoped regime.