title: Symmetry and magnitude of spin-orbit torques in ferromagnetic heterostructures.
abstract: Recent demonstrations of magnetization switching induced by in-plane current injection in heavy metal/ferromagnetic heterostructures have drawn increasing attention to spin torques based on orbital-to-spin momentum transfer. The symmetry, magnitude and origin of spin-orbit torques (SOTs), however, remain a matter of debate. Here we report on the three-dimensional vector measurement of SOTs in AlOx/Co/Pt and MgO/CoFeB/Ta trilayers using harmonic analysis of the anomalous and planar Hall effects. We provide a general scheme to measure the amplitude and direction of SOTs as a function of the magnetization direction. Based on space and time inversion symmetry arguments, we demonstrate that heavy metal/ferromagnetic layers allow for two different SOTs having odd and even behaviour with respect to magnetization reversal. Such torques include strongly anisotropic field-like and spin transfer-like components, which depend on the type of heavy metal layer and annealing treatment. These results call for SOT models that go beyond the spin Hall and Rashba effects investigated thus far.
authors.affiliation: Catalan Institute of Nanoscience and Nanotechnology (ICN2), E-08193 Barcelona, Spain. kevin.garello@mat.ethz.ch
authors.forename: Kevin
authors.initials: K
authors.lastname: Garello
authors.forename: Ioan Mihai
authors.initials: IM
authors.lastname: Miron
authors.forename: Can Onur
authors.initials: CO
authors.lastname: Avci
authors.forename: Frank
authors.initials: F
authors.lastname: Freimuth
authors.forename: Yuriy
authors.initials: Y
authors.lastname: Mokrousov
authors.forename: Stefan
authors.initials: S
authors.lastname: Blügel
authors.forename: Stéphane
authors.initials: S
authors.lastname: Auffret
authors.forename: Olivier
authors.initials: O
authors.lastname: Boulle
authors.forename: Gilles
authors.initials: G
authors.lastname: Gaudin
authors.forename: Pietro
authors.initials: P
authors.lastname: Gambardella
references.citation: Nat Nanotechnol. 2011 May 22;6(7):413-7
references.pmid: 21602814
references.citation: Science. 2012 May 4;336(6081):555-8
references.pmid: 22556245
references.citation: Phys Rev Lett. 2012 Aug 31;109(9):096602
references.pmid: 23002867
references.citation: Nat Mater. 2010 Mar;9(3):230-4
references.pmid: 20062047
references.citation: Phys Rev Lett. 2013 Jan 4;110(1):016805
references.pmid: 23383824
references.citation: Nature. 2010 Mar 11;464(7286):262-6
references.pmid: 20220845
references.citation: Phys Rev Lett. 2012 Mar 16;108(11):117201
references.pmid: 22540504
references.citation: Phys Rev Lett. 2011 Jan 21;106(3):036601
references.pmid: 21405285
references.citation: Nat Mater. 2012 Apr 23;11(5):372-81
references.pmid: 22522637
references.citation: Nat Mater. 2007 Nov;6(11):813-23
references.pmid: 17972936
references.citation: Nat Mater. 2012 Dec;11(12):1028-31
references.pmid: 23064497
references.citation: Nat Mater. 2013 Mar;12(3):240-5
references.pmid: 23263641
references.citation: Phys Rev Lett. 2010 Sep 17;105(12):126602
references.pmid: 20867663
references.citation: Phys Rev Lett. 2002 Jun 10;88(23):236601
references.pmid: 12059385
references.citation: Nature. 2011 Aug 11;476(7359):189-93
references.pmid: 21804568
references.citation: Phys Rev Lett. 2009 Apr 3;102(13):137202
references.pmid: 19392398
references.citation: Nat Mater. 2011 Jul 03;10(9):660-4
references.pmid: 21725322