Anisotropic Hanle lineshape via anisotropic magnetothermoelectric phenomena

TL;DR

This study reveals that anisotropic Hanle lineshape in metallic spin valves is primarily due to magneto-thermal effects, specifically anisotropic modulation of thermoelectric coefficients, challenging the conventional spin relaxation interpretation.

Contribution

It demonstrates that anisotropic Hanle lineshape arises from magnetothermoelectric phenomena, not solely from anisotropic spin relaxation times, highlighting the importance of thermoelectric effects in spin transport studies.

Findings

Anisotropic Hanle lineshape observed in metallic spin valves.

Thermoelectric modeling shows magneto-thermal origin of anisotropy.

Results suggest reconsideration of spin relaxation interpretations.

Abstract

We observe anisotropic Hanle lineshape with unequal in-plane and out-of-plane non-local signals for spin precession measurements carried out on lateral metallic spin valves with transparent interfaces. The conventional interpretation for this anisotropy corresponds to unequal spin relaxation times for in-plane and out-of-plane spin orientations as for the case of 2D materials like graphene, but it is unexpected in a polycrystalline metallic channel. Systematic measurements as a function of temperature and channel length, combined with both analytical and numerical thermoelectric transport models, demonstrate that the anisotropy in the Hanle lineshape is magneto-thermal in origin, caused by the anisotropic modulation of the Peltier and Seebeck coefficients of the ferromagnetic electrodes. Our results call for the consideration of such magnetothermoelectric effects in the study of anisotropic spin relaxation.