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▼ [19p-D104-4] Enhancement of spin-orbit torque in Co/CoOx/Pt structures
Keywords:spin-orbit torque, oxidization, spin current
Enhancement of current-induced torques on magnetization, including spin-orbit torque (SOT) in ferromagnet/heavy-metal bilayer structure, is crucial for magnetic memories operating with an electrical current. Our group has previously reported the enhancement of the field-like (FL) SOT in a Pt/Co system by oxidizing the Co surface (Pt/Co/CoOx structures). In this study, the effect of the oxidation was investigated using Co/CoOx/Pt structures, in which the Pt layer as a spin current source was directly deposited on the oxidized Co surface, to understand the role of the oxidized interface.
Ta(3.0 nm)/Pd(3.0)/Co(tCo) structures were deposited from the bottom side on the thermally oxidized Si substrate. Subsequently, the Co surface was exposed to the air in order to form CoOx layer (oxidized sample). After that, the 2.7-nm thick Pt layer was deposited onto it. From the measurement of the saturation magnetic moment, the CoOx thickness in this study was determined to be ~0.8 nm. The similar structure without CoOx layer (un-oxidized sample) was also prepared as a reference.
SOTs in un-oxidized and oxidized samples with several Co thickness were determined by the harmonic Hall voltage measurement. As a result, the DL torque for the oxidized sample was clearly larger than that for the un-oxidized sample even though the CoOx layer existed between the Co and Pt layers. We also confirmed that the FL torque was larger in the oxidized sample. The enhancement of the SOT by inserting the oxidization layer to the interface of the ferromagnet/heavy-metal bilayer structure is expected to provide a new information on the physics of the SOT.
Ta(3.0 nm)/Pd(3.0)/Co(tCo) structures were deposited from the bottom side on the thermally oxidized Si substrate. Subsequently, the Co surface was exposed to the air in order to form CoOx layer (oxidized sample). After that, the 2.7-nm thick Pt layer was deposited onto it. From the measurement of the saturation magnetic moment, the CoOx thickness in this study was determined to be ~0.8 nm. The similar structure without CoOx layer (un-oxidized sample) was also prepared as a reference.
SOTs in un-oxidized and oxidized samples with several Co thickness were determined by the harmonic Hall voltage measurement. As a result, the DL torque for the oxidized sample was clearly larger than that for the un-oxidized sample even though the CoOx layer existed between the Co and Pt layers. We also confirmed that the FL torque was larger in the oxidized sample. The enhancement of the SOT by inserting the oxidization layer to the interface of the ferromagnet/heavy-metal bilayer structure is expected to provide a new information on the physics of the SOT.