Deterministic spin-orbit torque switching of epitaxial ferrimagnetic insulator with perpendicular magnetic anisotropy fabricated by on-axis magnetron sputtering

Abstract Current-induced switching of magnetization states in ferromagnet/spin-orbit material heterostructures has attracted significant attention, driven by the increasing need for low power consumption and a more efficient mechanism for magnetization switching. However, current shunting for the used metallic ferromagnets remains challenging in achieving low switching current densities. Thulium iron garnet, Tm 3 Fe 5 O 12 (TmIG), is promising for such devices as it exhibits strong perpendicular magnetic anisotropy (PMA) and fast magnetization dynamics. However, there still remains a technological challenge in the growth of TmIG films using industry-compatible magnetron sputtering in a simple on-axis geometry for spintronic device applications. Here, we demonstrated the spin-orbit torque (SOT) magnetization switching of TmIG thin film grown by on-axis radio-frequency magnetron sputtering. Robust and deterministic SOT magnetization switching is achieved using TmIG/Pt heterostructures at a current density as low as $$0.7\times {10}^{11}\,{\rm{A}}/{{\rm{m}}}^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>0.7</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>11</mml:mn> </mml:mrow> </mml:msup> <mml:mspace/> <mml:mi>A</mml:mi> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi>m</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> . Anomalous Hall and second harmonic Hall measurements were performed to quantify effective spin-orbit fields. The effective field inducing damping-like torque is estimated to be 21±1 Oe per 10 7 A/cm 2 , higher than previous reports. These findings show a growth method for ferrimagnetic insulators with strong PMA in industry-compatible on-axis sputtering methods and its utilization for achieving energy-efficient SOT non-volatile memory applications.