VP12-01 In-plane magnetic field dependence of torque exerted on a domain wall in Pd/Co2MnGa
Creators: Takaya Koyama
Yuki Nishioka
Tetsuya Uemura
Michihiko Yamanouchi
Publisher: name: IEEE
Year: 2025

A heavy metal/a Weyl ferromagnet bilayers are promising for efficient current-induced domain wall (DW) motion because one can use both topological Hall torque (THT) induced by Weyl electrons in the Weyl ferromagnet [1] and spin-orbit torque (SOT) originating from the spin Hall effect in the heavy metal to move DWs. In this work, we investigated the in-plane magnetic field dependence of torque exerted on the DW to clarify the mechanism of current-induced DW motion in a perpendicularly magnetized bilayer composed of heavy metal Pd and Weyl ferromagnet Co2MnGa (CMG). Pd (3.0 nm) / CMG (1.8 nm) was deposited on an MgO (001) substrate. The stack was processed into a Hall-bar structure with a 2-µm wide channel and a pair of Hall probes. After preparing a DW in the channel, the DW position was monitored by measuring the transverse resistance while sweeping a perpendicular magnetic field under a constant current and in-plane magnetic field (Hx) along the channel direction. The coercive field required to propagate the DW through the probes varied almost linearly with current under Hx, which indicates an effective perpendicular magnetic field (Heff) was exerted on the DW by current. From the linear slope, efficiency (ηJ) of Heff generation per unit current density was evaluated. The value of ηJ showed the local maximum at μ0Hx = 10 mT and decreased monotonically at large | μ0Hx|, where μ0 is the permeability of the vacuum. On the other hand, ηJ originating from SOT, which is derived by measuring the hysteresis loop shift, varied almost linearly with respect to Hx at low |Hx| and saturated at large |Hx| in a heavy metal/a conventional ferromagnet bilayers, as reported previously [2]. These results indicate that the observed current-induced DW motion cannot be explained only by the contribution of SOT and the other torque such as the THT can be exerted on DW in Pd/CMG. This work was supported in part by JSPS KAKENHI (22K18961), MEXT X-NICS (JPJ011438), MEXT ARIM (JPMXP1224HK0020), and JST CREST (JPMJCR22C2).References: [1] Y. Araki and J. Ieda, Phys. Rev. Lett. 127, 277205 (2021). [2] C. Pai, et al., Phys. Rev. B 93, 14409 (2016).
A heavy metal/a Weyl ferromagnet bilayers are promising for efficient current-induced domain wall (DW) motion because one can use both topological Hall torque (THT) induced by Weyl electrons in the Weyl ferromagnet [1] and spin-orbit torque (SOT) originating from the spin Hall effect in the heavy metal to move DWs. In this work, we investigated the in-plane magnetic field dependence of torque exerted on the DW to clarify the mechanism of current-induced DW motion in a perpendicularly magnetized bilayer composed of heavy metal Pd and Weyl ferromagnet Co2MnGa (CMG). Pd (3.0 nm) / CMG (1.8 nm) was deposited on an MgO (001) substrate. The stack was processed into a Hall-bar structure with a 2-µm wide channel and a pair of Hall probes. After preparing a DW in the channel, the DW position was monitored by measuring the transverse resistance while sweeping a perpendicular magnetic field under a constant current and in-plane magnetic field (Hx) along the channel direction. The coercive field required to propagate the DW through the probes varied almost linearly with current under Hx, which indicates an effective perpendicular magnetic field (Heff) was exerted on the DW by current. From the linear slope, efficiency (ηJ) of Heff generation per unit current density was evaluated. The value of ηJ showed the local maximum at μ0Hx = 10 mT and decreased monotonically at large | μ0Hx|, where μ0 is the permeability of the vacuum. On the other hand, ηJ originating from SOT, which is derived by measuring the hysteresis loop shift, varied almost linearly with respect to Hx at low |Hx| and saturated at large |Hx| in a heavy metal/a conventional ferromagnet bilayers, as reported previously [2]. These results indicate that the observed current-induced DW motion cannot be explained only by the contribution of SOT and the other torque such as the THT can be exerted on DW in Pd/CMG. This work was supported in part by JSPS KAKENHI (22K18961), MEXT X-NICS (JPJ011438), MEXT ARIM (JPMXP1224HK0020), and JST CREST (JPMJCR22C2).References: [1] Y. Araki and J. Ieda, Phys. Rev. Lett. 127, 277205 (2021). [2] C. Pai, et al., Phys. Rev. B 93, 14409 (2016).