Ferromagnetism within the periodic Anderson model: A new approximation scheme

TL;DR

This paper introduces a new approximation scheme for the periodic Anderson model, enabling detailed analysis of magnetic properties across different regimes, revealing that ferromagnetism arises from an effective f-band rather than spin-spin interactions.

Contribution

A novel approach mapping the periodic Anderson model onto an effective Hubbard model, allowing comprehensive study of magnetic behavior in various regimes.

Findings

Ferromagnetism in the intermediate valence regime is linked to an effective f-band.

The hybridization gap significantly influences magnetic properties.

Magnetic ordering is not mediated by conduction electron spin-spin interactions.

Abstract

We introduce a new approach to the periodic Anderson model (PAM) that allows a detailed investigation of the magnetic properties in the Kondo as well as the intermediate valence regime. Our method is based on an exact mapping of the PAM onto an effective medium strong-coupling Hubbard model. For the latter, the so-called spectral density approach (SDA) is rather well motivated since it is based on exact results in the strong coupling limit. Besides the T=0 phase diagram, magnetization curves and Curie temperatures are presented and discussed with help of temperature-dependent quasiparticle densities of state. In the intermediate valence regime, the hybridization gap plays a major role in determining the magnetic behaviour. Furthermore, our results indicate that ferromagnetism in this parameter regime is not induced by an effective spin-spin interaction between the localized levels mediated by conduction electrons as it is the case in the Kondo regime. The magnetic ordering is rather a single band effect within an effective f-band.