Ferromagnetism in itinerant two-dimensional t2g systems

TL;DR

This paper proposes a novel mechanism for ferromagnetism in two-dimensional itinerant t2g systems, emphasizing orbital effects and non-perturbative interactions near the band bottom, relevant to transition metal oxide heterostructures.

Contribution

It introduces a new ferromagnetism mechanism independent of local moment coupling, focusing on orbital band structure and quasi-one-dimensional effects in 2D systems.

Findings

Ferromagnetism can arise from orbital band effects near the band bottom.

The quasi-one-dimensional limit allows exact thermodynamic solutions.

Potential relevance to ferromagnetic instabilities in t2g systems.

Abstract

Motivated by the recent indications of ferromagnetism in transition metal oxide heterostructures, we propose a possible mechanism to generate ferromagnetism for itinerant t2g systems in two spatial dimensions that does not rely on the coupling between local moments and conduction electrons. We particularly emphasize the orbital nature of different bands and show that, when the Fermi level lies near the bottom of the upper bands, a non-perturbative interaction effect due to the quasi-one-dimensional nature of the upper bands may drive a transition to a state in which the upper bands are ferromagnetically polarized. In the quasi-one-dimensional limit, the full thermodynamics may be obtained exactly. We discuss the connection between our mechanism with several itinerant t2g systems that may have ferromagnetic instabilities.