Quantum ferromagnetic transition in disordered itinerant electron systems

TL;DR

This paper develops an effective field theory for the quantum ferromagnetic transition in disordered electron systems, revealing unique scaling behavior and long-range interactions induced by static disorder at zero temperature.

Contribution

It introduces a novel effective field theory capturing the impact of disorder on quantum ferromagnetic transitions, with exact determination of the critical scaling behavior.

Findings

Disorder induces a 1/r^(2d-2) long-range interaction between spins.

The quantum critical point exhibits unusual scaling behavior.

Crossover to classical behavior is observable in low Curie temperature materials.

Abstract

An effective field theory is derived for the ferromagnetic transition of diffusive electrons at T=0. The static disorder which leads to diffusive electron dynamics induces an effective long-range interaction between the spins of the form 1/r^(2d-2). This leads to unusual scaling behavior at the quantum critical point, which is determined exactly. The crossover from this quantum fixed point to the classical Heisenberg fixed point should be observable in ferromagnetic materials with low Curie temperatures.