Spin-Orbit Torque and Interfacial Dzyaloshinskii-Moriya Interaction in Heavy Metal/Ferrimagnetic Insulator Deposited by Magnetron Sputtering

Ferrimagnetic insulators (FMIs) have abundant advantages for the application in spintronic devices, which have attracted intensive studies. However, in most previous studies on heavy metal (HM)/FMI bilayers, the FMI layers are deposited by pulsed laser deposition (PLD), and the HM layers are deposited by magnetron sputtering. This will cause the interfacial contamination due to the inevitable vacuum breaking, and then significantly affect the spin-orbit torque (SOT) generation and the Dzyaloshinskii-Moriya interaction (DMI) in the HM/FMI bilayers. In this work, the SOT and DMI in the HM/FMI bilayers deposited by magnetron sputtering without vacuum breaking are studied. The successful fabrication of the Tm3Fe5O12 (TmIG) layer, a typical FMI, with good crystallinity and perpendicular magnetic anisotropy (PMA) by magnetron sputtering is first demonstrated. Then by systematically varying the TmIG thickness, the SOT and DMI in the Pt/TmIG bilayers are studied. It is shown that the effective spin Hall angle in the Pt/TmIG bilayers is much larger than most previously reported values. It is further demonstrated that the DMI constant scales linearly with the inverse of the TmIG thickness, indicating the interfacial origin of the DMI. The study provides a piece of information for the basic understandings of the SOT and DMI in the HM/FMI bilayers.