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, and 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 and Cu), which present the standard anisotropic magnetoresistance expected from polycrystalline FM layers. In the Ta, W, and 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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9 November 2015
Research Article|
November 12 2015
Magnetoresistance of heavy and light metal/ferromagnet bilayers
Can Onur Avci
;
Can Onur Avci
Department of Materials,
ETH Zürich
, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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Kevin Garello;
Kevin Garello
Department of Materials,
ETH Zürich
, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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Johannes Mendil;
Johannes Mendil
Department of Materials,
ETH Zürich
, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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Abhijit Ghosh;
Abhijit Ghosh
Department of Materials,
ETH Zürich
, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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Nicolas Blasakis;
Nicolas Blasakis
Department of Materials,
ETH Zürich
, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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Mihai Gabureac;
Mihai Gabureac
Department of Materials,
ETH Zürich
, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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Morgan Trassin;
Morgan Trassin
Department of Materials,
ETH Zürich
, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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Manfred Fiebig;
Manfred Fiebig
Department of Materials,
ETH Zürich
, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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Pietro Gambardella
Pietro Gambardella
Department of Materials,
ETH Zürich
, Hönggerbergring 64, CH-8093 Zürich, Switzerland
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Appl. Phys. Lett. 107, 192405 (2015)
Article history
Received:
September 04 2015
Accepted:
October 25 2015
Citation
Can Onur Avci, Kevin Garello, Johannes Mendil, Abhijit Ghosh, Nicolas Blasakis, Mihai Gabureac, Morgan Trassin, Manfred Fiebig, Pietro Gambardella; Magnetoresistance of heavy and light metal/ferromagnet bilayers. Appl. Phys. Lett. 9 November 2015; 107 (19): 192405. https://doi.org/10.1063/1.4935497
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