Intrinsic mechanism for anisotropic magnetoresistance and experimental confirmation in Co$_x$Fe$_{1-x}$ single-crystal films

TL;DR

This study predicts and confirms that anisotropic magnetoresistance in CoFe alloys depends on current direction and composition, with an intrinsic mechanism linked to band crossing and symmetry, enabling tunability.

Contribution

It introduces an intrinsic mechanism for AMR based on band crossing and symmetry protection, supported by first-principles calculations and experimental validation.

Findings

AMR depends on current orientation and alloy composition.

Intrinsic AMR mechanism arises from band crossing due to symmetry.

Transport measurements confirm the predicted AMR behavior.

Abstract

Using first-principles transport calculations, we predict that the anisotropic magnetoresistance (AMR) of single-crystal Co$_x$Fe$_{1-x}$ alloys is strongly dependent on the current orientation and alloy concentration. An intrinsic mechanism for AMR is found to arise from the band crossing due to magnetization-dependent symmetry protection. These special $k$-points can be shifted towards or away from the Fermi energy by varying the alloy composition and hence the exchange splitting, thus allowing AMR tunability. The prediction is confirmed by delicate transport measurements, which further reveal a reciprocal relationship of the longitudinal and transverse resistivities along different crystal axes.