Variational Mote Carlo Study of Flat Band Ferromagnetism -- Application to CeRh_3 B_2

TL;DR

This paper introduces a variational Monte Carlo approach to study flat band ferromagnetism, proposing a new mechanism in CeRh_3B_2 involving hybridized 4f and conduction electrons leading to weak ferromagnetism.

Contribution

It presents a novel variational Monte Carlo analysis of flat band ferromagnetism in CeRh_3B_2, highlighting the role of hybridization and spin-orbit interaction in stabilizing ferromagnetism.

Findings

Ferromagnetism is stabilized by a nearly flat band of hybridized states.

Magnetic moments from 4f and conduction electrons tend to cancel.

The Fermi surface remains largely unaffected by 4f electrons.

Abstract

A new mechanism for ferromagnetism in CeRh_3B_2 is proposed on the basis of variational Monte Carlo results. In a one-dimensional Anderson lattice where each 4f electron hybridizes with a ligand orbital between neighboring Ce sites, ferromagnetism is stabilized due to a nearly flat band which is a mixture of conduction and 4f electron states. Because of the strong spin-orbit interaction in 4f electron states, and of considerable amount of hybridization in the nearly flat band, the magnetic moments from 4f and conduction electrons tend to cancel each other. The resultant ferromagnetic moment becomes smaller as compared with the local 4f moment, and the Fermi surface in the ferromagnetic ground state is hardly affected by the presence of 4f electrons. These theoretical results are consistent with experimental observations in CeRh_3B_2 by neutron scattering and dHvA effects.