Magnetically-driven electronic phase separation in the semimetallic ferromagnet EuB$_6$

TL;DR

This study provides direct evidence of magnetically-driven electronic phase separation in EuB$_6$, revealing how magnetic polarons form conducting clusters that percolate at a critical magnetization, affecting transport properties.

Contribution

It introduces a comprehensive scenario for magnetic polaron percolation in EuB$_6$, linking magnetic order, phase separation, and transport phenomena.

Findings

Magnetic polarons form conducting clusters in EuB$_6$

Percolation occurs at a critical magnetization level

Transport properties are affected by phase separation

Abstract

From measurements of fluctuation spectroscopy and weak nonlinear transport on the semimetallic ferromagnet EuB$_6$ we find direct evidence for magnetically-driven electronic phase separation consistent with the picture of percolation of magnetic polarons (MP), which form highly conducting magnetically-ordered clusters in a paramagnetic and 'poorly conducting' background. These different parts of the conducting network are probed separately by the noise spectroscopy/nonlinear transport and the conventional linear resistivity. We suggest a comprehensive and 'universal' scenario for the MP percolation, which occurs at a critical magnetization either induced by ferromagnetic order at zero field or externally applied magnetic fields in the paramagentic region.