Two types of colossal magnetoresistance with distinct mechanisms in Eu5In2As6

TL;DR

This paper uncovers two distinct mechanisms of colossal magnetoresistance in Eu5In2As6, linking them to magnetic polaron percolation and charge order melting, providing a unified understanding of CMR phenomena.

Contribution

It demonstrates the coexistence of two CMR types in a single material and proposes their underlying mechanisms, advancing the understanding of CMR in magnetic semiconductors.

Findings

Peak-type CMR attributed to magnetic polaron percolation

Upturn-type CMR linked to melting of charge order

Proposes a unified framework for different CMR mechanisms

Abstract

Recent reports of colossal negative magnetoresistance (CMR) in a few magnetic semimetals and semiconductors have attracted attention, because these materials are devoid of the conventional mechanisms of CMR such as mixed valence, double exchange interaction, and Jahn-Teller distortion. New mechanisms have thus been proposed, including topological band structure, ferromagnetic clusters, orbital currents, and charge ordering. The CMR in these compounds has been reported in two forms: either a resistivity peak or a resistivity upturn suppressed by a magnetic field. Here we reveal both types of CMR in a single antiferromagnetic semiconductor Eu5In2As6. Using the transport and thermodynamic measurements, we demonstrate that the peak-type CMR is likely due to the percolation of magnetic polarons with increasing magnetic field, while the upturn-type CMR is proposed to result from the melting of a charge order under the magnetic field. We argue that similar mechanisms operate in other compounds, offering a unifying framework to understand CMR in seemingly different materials.