Fourfold Symmetry of Anisotropic Magnetoresistance in Epitaxial Fe3O4 Thin Films

TL;DR

This study reveals that epitaxial Fe3O4 thin films exhibit a fourfold symmetric anisotropic magnetoresistance (AMR) linked to lattice symmetry, with temperature-dependent behavior and distinct origins from the planar Hall effect.

Contribution

It demonstrates the fourfold symmetry of AMR in Fe3O4 films and clarifies its relation to lattice symmetry rather than spin scattering, expanding understanding of AMR mechanisms.

Findings

AMR shows both twofold and fourfold symmetry components.

Fourfold AMR is related to lattice symmetry, not spin scattering.

Temperature affects the competition between AMR components.

Abstract

We studied the angular dependence of anisotropic magnetoresistance (AMR) and Planar Hall effect (PHE) at various temperatures in high quality epitaxial Fe3O4 films grown on MgO(001) substrates. The PHE contains only a twofold angular dependence, but the AMR below 200K is constituted with both twofold and fourfold symmetric terms. A quantitative fitting based on a phenomenological model indicates the nonmonotonics temperature dependence of the twofold component of AMR can be ascribed to the competition between the term and the term. A unidirectional component was observed in the angular dependent AMR. The fourfold symmetric AMR also existed for the magnetic field rotating in the plane perpendicular to the current. Our results indicate the AMR and PHE in single crystalline films have different origins, and also prove that the origin of the four-fold symmetry of AMR is related to the lattice symmetry rather than the spin scattering near the antiphase boundaries.