Probing intrinsic magnetization dynamics of the Y3Fe5O12/Bi2Te3 interface at low temperature

Topological insulator–magnetic insulator (TI–MI) heterostructures hold significant promise in the field of spintronics, offering the potential for manipulating magnetization through topological surface state–enabled spin-orbit torque. However, many TI–MI interfaces are plagued by issues such as contamination within the magnetic insulator layer and the presence of a low-density transitional region of the topological insulator. These interfacial challenges often obscure the intrinsic behavior of the TI–MI system. In this study, we addressed these challenges by depositing sputtered ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ on liquid phase epitaxy grown ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}/{\mathrm{Gd}}_3{\mathrm{Ga}}_5{\mathrm{O}}_{12}$. The liquid phase epitaxy grown ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ has been previously shown to have exceptional interface quality, without an extended transient layer derived from interdiffusion processes of the substrate or impurity ions, thereby eliminating rare-earth impurity-related losses in the MI at low temperatures. At the TI–MI interface, high-resolution depth-sensitive polarized neutron reflectometry confirmed the absence of a low-density transitional growth region of the TI. By overcoming these undesirable interfacial effects, we isolate and probe the intrinsic low-temperature magnetization dynamics and transport properties of the TI–MI interface. Our findings revealed strong spin pumping at low temperatures, accompanied by an additional in-plane anisotropy. The enhanced spin pumping at low temperatures is correlated with the observed suppression of bulk conduction and the weak antilocalization in the TI film, highlighting the interplay between the transport and spin pumping behavior in the TI–MI system.