Temperature dependence of the magnetic hyperfine field at an s-p impurity diluted in $R$Ni$_{2}$

TL;DR

This study investigates how temperature affects the magnetic hyperfine field at an s-p impurity in intermetallic RNi2 compounds, focusing on the role of 4f electrons and effective R-ion lattices.

Contribution

It introduces a theoretical model that simplifies the host to an effective R-ion lattice with d electrons, incorporating temperature effects on magnetic hyperfine fields.

Findings

Temperature influences the magnetic hyperfine field at the impurity.

The model captures the polarization effects of 4f electrons on the d band.

The approach provides a framework for understanding impurity magnetism in intermetallics.

Abstract

We study the formation of local magnetic moments and magnetic hyperfine fields at an \textit{s-p} impurity diluted in intermetallic Laves phases compounds $R$Ni$_{2}$ ($R$ = Nd, Sm, Gd, Tb, Dy) at finite temperatures. We start with a clean host and later the impurity is introduced. The host has two-coupled ($R$ and Ni) sublattice Hubbard Hamiltonians but the Ni sublattice can be disregarded because its $\textit{d}$ band, being full, is magnetically ineffective. Also, the effect of the $\textit{4f}$ electrons of $R$ is represented by a polarization of the \textit{d} band that would be produced by the $\textit{4f}$ magnetic field.This leaves us with a lattice of \textit{effective} rare earth \textit{R}-ions with only \textit{d} electrons. For the \textit{dd} electronic interaction we use the Hubbard-Stratonovich identity in a functional integral approach in the static saddle point approximation.