Quantum Griffiths effects in itinerant Heisenberg magnets

2004/05/31 by Thomas Vojta, Joerg Schmalian · 2 citations
Physics and Astronomy · #cond-mat.str-el #cond-mat.dis-nn

paper · pdf · doi:10.1103/physrevb.72.045438

published as Phys. Rev. B 72, 045438 (2005) · 6 pages, 1 eps figure, final version as published

arxiv created 2005/07/19 · arxiv updated 2009/12/01

Abstract

We study the influence of quenched disorder on quantum phase transitions in itinerant magnets with Heisenberg spin symmetry, paying particular attention to rare disorder fluctuations. In contrast to the Ising case where the overdamping suppresses the tunneling of the rare regions, the Heisenberg system displays strong power-law quantum Griffiths singularities in the vicinity of the quantum critical point. We discuss these phenomena based on general scaling arguments, and we illustrate them by an explicit calculation for O(N) spin symmetry in the large-N limit. We also discuss broad implications for the classification of quantum phase transitions in the presence of quenched disorder.

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• A unified equation for saturation magnetization and spin transport in weakly disordered ferromagnets

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