Itinerant ferromagnetism in a spin-fermion model for diluted spin systems

TL;DR

This paper studies itinerant ferromagnetism in a diluted spin-fermion model derived from the Hubbard model, focusing on how carrier density and disorder influence magnetic and transport properties, with implications for diluted magnetic semiconductors.

Contribution

It introduces a semi-classical Monte Carlo approach to analyze ferromagnetism and transport in a disordered spin-fermion system beyond perturbative regimes.

Findings

Ferromagnetic transition temperature optimizes with carrier density.

Transport properties correlate directly with magnetic behavior.

Results provide insights into ferromagnetism in diluted magnetic semiconductors.

Abstract

We investigate the itinerant ferromagnetism using a diluted spin-fermion model, derived from a repulsive Hubbard model, where itinerant fermions are coupled antiferromagnetically to auxiliary fields in a three-dimensional simple cubic lattice. We focus, in particular, on understanding the spin-dependent transport properties of the itinerant fermions in the impurity band by taking positional disorder of the auxiliary fields into account. For on-site repulsion $U$ $\sim$ bandwidth the density of the itinerant carriers confined to the impurity band, play a key role in determining the kinetic energy of the system and consequently the carrier spin polarization. Our semi-classical Monte Carlo calculations show that the ferromagnetic transition temperature of the carrier spins indeed shows an optimization behavior with the carrier density. We calculate the transport properties in details to establish a one-to-one correspondence between the magnetic and transport properties of the carriers. Our results obtained beyond the perturbative regime are significant for understanding the ferromagnetism in diluted magnetic semiconductors.