Proximity Magnetism in Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3/MnTe Natural Heterostructures

TL;DR

This study uncovers naturally formed Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3/MnTe heterostructures that exhibit enhanced magnetic and topological properties, enabling efficient spin-orbit torque switching for spintronic applications.

Contribution

It demonstrates the formation of self-organized Mn(Bi,Sb)2Te4 lamellae in heterostructures and their role in mediating exchange coupling and spin-orbit torque effects.

Findings

Mn(Bi,Sb)2Te4 stabilizes as self-organized lamellae in heterostructures.

Interfacial Neel temperature exceeds 200 K, much higher than Mn(Bi,Sb)2Te4's own TN.

Achieved low critical current density for spin-orbit torque switching (300 kA/cm²).

Abstract

Magnetic topological insulators and their heterostructures provide great opportunities in coupling band topology with nontrivial spin configuration for enhanced spintronic device performance as well as designing totally new magnetoelectric systems and functionalities. We find that Mn interdiffusion from MnTe when interfaced with (Bi,Sb)2Te3 stabilizes as self-organized Mn(Bi,Sb)2Te4 septuple lamellae amongst alternating (Bi,Sb)2Te3 quintuple layers, as observed using scanning transmission electron microscopy and depth-sensitive polarized neutron reflectometry. We further demonstrate a valuable combination of magnetic and topological orders in these naturally formed Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3 heterostructures that are exchange coupled with MnTe. Magnetotransport experiments and quantum magnetism simulations reveal that, above its own Neel temperature TN of 20 K, Mn(Bi,Sb)2Te4 mediates the exchange field leading to an anomalous Hall effect at the (Bi,Sb)2Te3/MnTe interface, with an enhanced interfacial TN exceeding 200 K. This novel magnetic interface in turn allows a robust and deterministic spin-orbit torque switching without an external magnetic field at a low critical current density of 300 kA cm-2. The antiferromagnetically coupled architecture of Mn(Bi,Sb)2Te4-(Bi,Sb)2Te3/MnTe, featuring unique magnetic and topological proximity effects across a chalcogenide backbone, is rich in fundamental interface physics and holds potential for practical applications in spintronics.