Ferromagnetic Ground States in Face-Centered Cubic Hubbard Clusters.

T X R Souza,C A Macedo,Elena A Rozhkova

doi:10.1371/journal.pone.0161549

Abstract

In this study, the ground state energies of face-centered cubic Hubbard clusters are analyzed using the Lanczos method. Examination of the ground state energy as a function of the number of particle per site n showed an energy minimum for face-centered cubic structures. This energy minimum decreased in n with increasing coulombic interaction parameter U. We found that the ground state energy had a minimum at n = 0.6, when U = 3W, where W denotes the non-interacting energy bandwidth and the face-centered cubic structure was ferromagnetic. These results, when compared with the properties of nickel, shows strong similarity with other finite temperature analyses in the literature and supports the Hirsh’s conjecture that the interatomic direct exchange interaction dominates in driving the system into a ferromagnetic phase.

Highlights

The Hubbard model [1] is the most powerful model for studying the strongly correlated electrons in transition metals
We analyzed the electronic correlations in the fcc clusters using the single-band Hubbard model for several coulombic interaction regimes defined by U/t
For U/t = 3W, where W is the non-interacting energy bandwidth, the ground-state energy as a function of the particle density reached a minimum value at n = 0.6

Summary

Introduction

The Hubbard model [1] is the most powerful model for studying the strongly correlated electrons in transition metals In some of these metals the d-orbitals are only partially filled, and in the ferromagnetic state, the magnetic moment per atom is a fraction of the Bohr magneton (μB). The transition metals have narrow energy bands owing to the degeneracy of their d-orbitals and it is possible to use a single-band Hubbard model to study them. This model has two contributing terms: the first one represents electronic hopping, commonly considered only between the nearest neighbors, and the second term represents the intra-atomic coulombic interaction.

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Methods

Conclusion