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

Abstract

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.

Giant Orbital-to-Spin Conversion for Efficient Current-Induced Magnetization Switching of Ferrimagnetic Insulator

“…For instance, Ye et al reported a value of ξ DL = 0.029 in a Pt/ TmIG bilayer. 33 Avci et al reported a value of ξ DL ≈ 0.01 in a Pt/TmIG bilayer. 27 Chen et al reported a value of ξ DL = 0.011 in a Pt/Tb 3 Fe 5 O 12 (TbIG) bilayer.…”

“…Argon gas was applied for the deposition. The detail of the fabrication is described in our previous report . After cooling down to room temperature, Pt and Ta layers were deposited subsequently on the TmIG surface without breaking the vacuum.…”

“…This value is comparable to previously reported values of Pt/FMI bilayers. For instance, Ye et al reported a value of ξ DL = 0.029 in a Pt/TmIG bilayer . Avci et al reported a value of ξ DL ≈ 0.01 in a Pt/TmIG bilayer .…”

“…The detail of the fabrication is described in our previous report. 33 After cooling down to room temperature, Pt and Ta layers were deposited subsequently on the TmIG surface without breaking the vacuum. A 1-nm-thick SiO 2 capping layer was deposited from a SiO 2 target to protect the films from oxidation.…”

Field-free magnetization switching with full scale in Pt/Tm3Fe5O12 bilayer on vicinal substrate

“…One prominent category within FMI features ferrimagnetic rare-earth iron garnet, renowned for its low Gilbert damping, a Néel temperature exceeding RT, and robust perpendicular magnetic anisotropy (PMA) induced by magnetoelastic anisotropy, [5][6][7] which ensures low energy consumption and high-speed response in spintronic devices, [8][9][10][11][12] with Tm 3 Fe 5 O 12 (TmIG) being the most extensively studied among them. It has been seamlessly integrated into Pt/TmIG heterostructures, 8,[13][14][15] demonstrating the anticipated spin-orbit torques (SOTs), which offers an efficient and scalable method for electrically manipulating the magnetization of TmIG. Nevertheless, the switching of TmIG by SOT necessitates an external in-plane (IP) magnetic field (H x ) parallel to the longitudinal current direction, thereby impeding the progress of TmIG into practical applications.…”