VP1-01: Current-induced domain wall motion in Pd/Co2MnGa with perpendicular magnetic anisotropy

Reduction of current density required to move a domain wall (DW) is one of major issues for spintronics devices using current-induced DW motion. Perpendicularly magnetized Weyl ferromagnet is promising for such applications because efficient current-induced DW motion by Weyl electrons has been theoretically proposed [1] and demonstrated in a Weyl ferromagnet SrRuO3 at low temperature [2]. Toward practical applications of Weyl ferromagnet, we study current-induced DW motion in a perpendicularly magnetized Co2MnGa (CMG) because CMG is considered to be Weyl ferromagnet at room temperature [3]. Pd (2.5 nm) / CMG (1.6 nm) was deposited, from the surface side, on an MgO substrate, where the Pd layer was deposited to induce the perpendicular anisotropy in CMG [4]. The stack was processed into a Hall-bar structure with a 2-µm wide channel and a Au/Cr Oersted line. The transverse resistance showed a square hysteresis with respect to a perpendicular magnetic field, which indicates the CMG was perpendicularly magnetized. After preparing a DW in the channel by applying a current pulse to the Oersted line, successive current pulses with various amplitudes and 10 ms duration were applied to the channel under zero magnetic field at room temperature. When current density in Pd/CMG was higher than 2.9 x 107 A/cm2, the DW was moved by current in the direction opposite to current. Considering that current density in the CMG layer was two orders of magnitude lower than that in Pd/CMG from resistivity measurements, the observed DW motion cannot be explained by the conventional spin transfer torque and field-like torque in CMG. We measured the propagation field of the DW under a DC current to elucidate the mechanism. The propagation field varied almost linearly with current, which indicates current acts as an effective magnetic field driving the DW. These results suggest that torque induced by Weyl electrons and/or spin orbit torque originating from spin Hall effect in the Pd layer play an important role in the observed current-induced DW motion. This work was supported in part by JSPS KAKENHI (22K18961), MEXT X-NICS (JPJ011438), MEXT ARIM (JPMXP1222HK0071), and JST CREST (JPMJCR22C2).References: [1] Y. Araki and J. Ieda, Phys. Rev. Lett. 127, 277205 (2021). [2] M. Yamanouchi, et al., Sci. Adv. 8. 15 (2022). [3] Q. Wang, et al., Appl. Phys. Lett. 115, 252401 (2019). [4] B. M. Ludbrook et al., Appl. Phys. Lett. 110, 062408 (2017). [5] H. Jiajao et al., Appl. Phys. Lett. 119, 212409 (2021).