Magnetic and electronic inhomogeneity in Sm$_{1-x}$Eu$_x$B$_6$

TL;DR

This study explores the magnetic and electronic inhomogeneity in Sm$_{1-x}$Eu$_x$B$_6$, revealing complex magnetic behaviors and polaron formation that depend on Eu content, with implications for understanding magnetic polarons and topological insulators.

Contribution

It provides new insights into the interplay of magnetic order and polaron formation in Sm$_{1-x}$Eu$_x$B$_6$, especially at high Eu concentrations, through detailed magnetic and transport measurements.

Findings

Sm$_{0.01}$Eu$_{0.99}$B$_6$ behaves similarly to EuB$_6$.

Sm$_{0.05}$Eu$_{0.95}$B$_6$ shows antiferromagnetic order with local polarons.

Pronounced hysteresis in magnetoresistance at low temperature and specific magnetic fields.

Abstract

While SmB$_6$ attracts attention as a possible topological Kondo insulator, EuB$_6$ is known to host magnetic polarons that give rise to large magnetoresistive effects above its ferromagnetic order transition. Here we investigate single crystals of Sm$_{1-x}$Eu$_x$B$_6$ by magnetic and magnetotransport measurements to explore a possible interplay of these two intriguing phenomena, with focus on the Eu-rich substitutions. Sm$_{0.01}$Eu$_{0.99}$B$_6$ exhibits generally similar behavior as EuB$_6$. Interestingly, Sm$_{0.05}$Eu$_{0.95}$B$_6$ combines global antiferromagnetic order with local polaron formation. A pronounced hysteresis is found in the magnetoresistance of Sm$_{0.1}$Eu$_{0.9}$B$_6$ at low temperature ($T=$ 1.9 K) and applied magnetic fields between 2.3 $-$ 3.6 T. The latter is in agreement with a phenomenological model that predicts the stabilization of ferromagnetic polarons with increasing magnetic field within materials with global antiferromagnetic order.