Microscopic conditions favoring itinerant ferromagnetism: Hund's rule coupling and orbital degeneracy

TL;DR

This paper investigates how Hund's rule coupling and orbital degeneracy influence the stabilization of itinerant ferromagnetism using a two-band Hubbard model and quantum Monte Carlo simulations.

Contribution

It introduces a detailed phase diagram showing ferromagnetism over a wide range of fillings and explores orbital ordering at quarter filling.

Findings

Ferromagnetism occurs over a broad electron filling range.

Antiferromagnetism is confined near half filling.

Orbital ordering is possible at quarter filling.

Abstract

The importance of Hund's rule coupling for the stabilization of itinerant ferromagnetism is investigated within a two-band Hubbard model. The magnetic phase diagram is calculated by finite-temperature quantum Monte Carlo simulations within the dynamical mean-field theory. Ferromagnetism is found in a broad range of electron fillings whereas antiferromagnetism exists only near half filling. The possibility of orbital ordering at quarter filling is also analyzed.