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arXiv · 1510.06285

Magnetoresistance of heavy and light metal/ferromagnet bilayers

Can Onur Avci·Kevin Garello·Johannes Mendil·Abhijit Ghosh·Nicolas Blasakis·Mihai Gabureac·Morgan Trassin·Manfred Fiebig·Pietro Gambardella
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Abstract

We studied the magnetoresistance of normal metal (NM)/ferromagnet (FM) bilayers in the linear and nonlinear (current-dependent) regimes and compared it with the amplitude of the spin-orbit torques and thermally induced electric fields. Our experiments reveal that the magnetoresistance of the heavy NM/Co bilayers (NM = Ta, W, Pt) is phenomenologically similar to the spin Hall magnetoresistance (SMR) of YIG/Pt, but has a much larger anisotropy, of the order of 0.5%, which increases with the atomic number of the NM. This SMR-like behavior is absent in light NM/Co bilayers (NM = Ti, Cu), which present the standard AMR expected of polycrystalline FM layers. In the Ta, W, Pt/Co bilayers we find an additional magnetoresistance, directly proportional to the current and to the transverse component of the magnetization. This so-called unidirectional SMR, of the order of 0.005%, is largest in W and correlates with the amplitude of the antidamping spin-orbit torque. The unidirectional SMR is below the accuracy of our measurements in YIG/Pt.

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Can Onur Avci, Kevin Garello, Johannes Mendil, Abhijit Ghosh, Nicolas Blasakis, Mihai Gabureac, Morgan Trassin, Manfred Fiebig, Pietro Gambardella. 2015-10-21. Magnetoresistance of heavy and light metal/ferromagnet bilayers. https://doi.org/10.1063/1.4935497

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