Observation of High-Order Anisotropic Magnetoresistance in a Cubic Ferromagnet

TL;DR

This study reveals high-order anisotropic magnetoresistance (AMR) up to the 18th harmonic in cubic Fe(001) films, challenging previous assumptions and highlighting the role of crystal symmetry and microscopic scattering mechanisms.

Contribution

It demonstrates that high-order AMR terms are intrinsic and tunable, expanding understanding of spin-orbit transport in cubic ferromagnets.

Findings

High-order AMR observed up to 18th harmonic.

Six-fold and higher-order terms are intrinsic and symmetry-allowed.

High-order terms are tunable by temperature and thickness.

Abstract

High-order anisotropic magnetoresistance (AMR) is observed up to the 18th harmonic in cubic Fe(001) thin films, overturning the long-standing paradigm that only two- and four-fold terms are symmetry-allowed. Using angle-resolved transport and Fourier analysis, we show that six-fold and higher-order terms are intrinsic, tunable by temperature and thickness, and predicted by crystal symmetry. Microscopically, the two-fold sign reversal arises from a crossover between weak and strong scattering regimes, while high-order terms emerge from the interplay of anisotropic Fermi velocity and relaxation time. Our results establish high-order AMR as a symmetry-prescribed property of cubic ferromagnets, providing critical benchmarks for spin-orbit transport theory and enabling new angular-sensitive spintronic functionalities.