Field-induced metal-to-insulator transition and colossal anisotropic magnetoresistance in a nearly Dirac material EuMnSb$_2$

TL;DR

This study reports an unprecedented colossal anisotropic magnetoresistance (AMR) effect in EuMnSb$_2$, a nearly Dirac antiferromagnetic material, driven by a field-induced metal-insulator transition and strong spin-orbit coupling effects.

Contribution

The paper demonstrates a colossal AMR effect in EuMnSb$_2$ linked to Dirac-like band structure and magnetic structure, revealing new potential for antiferromagnetic spintronics applications.

Findings

Colossal AMR of 1.84×10^6% at 2 K observed.

Dirac-like band structure confirmed via density functional theory.

Field-induced MIT is crucial for the colossal AMR effect.

Abstract

How to realize applicably appreciated functionalities based on the coupling between charge and spin degrees of freedom is still a challenge in the field of spintronics. For example, anisotropic magnetoresistance (AMR) effect is utilized to read out the information stored by various magnetic structures, which usually originates from atomic spin-orbit coupling (SOC). However, the application of AMR in antiferromagnet-based spintronics is still hindered by rather small AMR value. Here, we discover a colossal AMR effect during the field-induced metal-to-insulator transition (MIT) in a nearly Dirac material EuMnSb$_2$ with an antiferromagnetic order of Eu$^{2+}$ moments. The colossal AMR reaches to an unprecedented value of 1.84$\times$10$^6$% at 2 K, which is four orders of magnitude larger than previously reported values in antiferromagnets. Based on density functional theory calculations, a Dirac-like band structure, which is strongly dependent on SOC, is confirmed around Y point and dominates the overall transport properties in the present sample with predominant electron-type carriers. Moreover, it is also revealed that the indirect band gap around Fermi level is dependent on the magnetic structure of Eu$^{2+}$ moments, which leads to the field-induced MIT and plays a key role on the colossal AMR effect. Finally, our present work suggests that the similar antiferromagnetic topological materials as EuMnSb$_2$, in which Dirac-like fermions is strongly modulated by SOC and antiferromagnetism, would be a fertile ground to explore applicably appreciated AMR effect.