Correlation Effects in Band Ferromagnetism

TL;DR

This paper investigates how on-site and inter-site electronic interactions influence the Curie temperature in transition metals, revealing their roles in promoting or suppressing ferromagnetism and aligning theoretical predictions with experimental data.

Contribution

It introduces a new approximation that accounts for inter-site interactions decreasing band width, improving the understanding of ferromagnetism in transition metals.

Findings

On-site Coulomb repulsion favors ferromagnetism at half-filling.

Inter-site interactions promote ferromagnetism at band edges.

The new model lowers the Curie temperature to match experimental values.

Abstract

We analyze the influence of different on-site and inter-site interactions on the Curie temperature of transition metal magnetic elements. The numerical calculations show the well known result that the on-site Coulomb repulsion helps ferromagnetism mainly at half-filling of the band, where the 3d elements are antiferromagnetic (Cr, Mn). The inter-site interactions, which in the new approximation decrease the width of the band, favor ferromagnetism at both ends of the band. At the same time they lower the ferromagnetic Curie temperature towards experimental values, removing the paradox which persisted for a long time.