Possible magnetic-polaron-switched positive and negative magnetoresistance in the GdSi single crystal

TL;DR

This study reveals that GdSi single crystals exhibit large, anisotropic positive and negative magnetoresistance linked to magnetic polarons and spin scattering, offering new pathways for designing advanced magnetic materials.

Contribution

It uncovers the magnetic-polaron mechanism behind MR switching in GdSi, a novel insight into AFM materials' magnetoresistive behavior.

Findings

Positive MR up to 415% in GdSi

Negative MR around -10.5% near T_N

Magnetic polarons induce positive MR

Abstract

Magnetoresistance (MR) has attracted tremendous attention for possible technological applications. Understanding the role of magnetism in manipulating MR may in turn steer the searching for new applicable MR materials. Here we show that antiferromagnetic (AFM) GdSi metal displays an anisotropic positive MR value (PMRV), up to $\sim$ 415%, accompanied by a large negative thermal volume expansion (NTVE). Around $T_\text{N}$ the PMRV translates to negative, down to $\sim$ -10.5%. Their theory-breaking magnetic-field dependencies [PMRV: dominantly linear; negative MR value (NMRV): quadratic] and the unusual NTVE indicate that PMRV is induced by the formation of magnetic polarons in 5$d$ bands, whereas NMRV is possibly due to abated electron-spin scattering resulting from magnetic-field-aligned local 4$f$ spins. Our results may open up a new avenue of searching for giant MR materials by suppressing the AFM transition temperature, opposite the case in manganites, and provide a promising approach to novel magnetic and electric devices.