Spiral magnetic order, non-uniform states and electron correlations in the conducting transition metal systems

TL;DR

This paper investigates the magnetic phase diagram of conducting transition metal systems using Hubbard and $s$-$d$ exchange models, incorporating electron correlations with advanced approximations to better understand magnetic states.

Contribution

It introduces a combined approach using Hartree-Fock and Kotliar-Ruckenstein slave boson approximations to accurately describe magnetic phases and electron correlations in transition metal systems.

Findings

Electron correlations lower the paramagnetic phase energy significantly.

Magnetic phase energies are reduced when electron correlations are included.

Differences between models with localized moments are discussed.

Abstract

The ground-state magnetic phase diagram is calculated within the Hubbard and $s$-$d$ exchange (Kondo) models for square and simple cubic lattices vs. band filling and interaction parameter. The difference of the results owing to the presence of localized moments in the latter model is discussed. We employ a generalized Hartree-Fock approximation (HFA) to treat commensurate ferromagnetic (FM), antiferromagnetic (AFM), and incommensurate (spiral) magnetic phases. The electron correlations are taken into account within the Hubbard model by using the Kotliar-Ruckenstein slave boson approximation (SBA). The main advantage of this approach is a correct qualitative description of the paramagnetic phase: its energy becomes considerably lower as compared with HFA, and the gain in the energy of magnetic phases is substantially reduced.