Effects of Crystalline Disorder on Interfacial and Magnetic Properties of Sputtered Topological Insulator/Ferromagnet Heterostructures

TL;DR

This study investigates how crystalline disorder in topological insulator films affects their interfacial and magnetic properties when coupled with ferromagnets, revealing disorder-dependent magnetic interactions and spintronic effects.

Contribution

It provides new insights into the impact of crystalline disorder on interfacial reactions, magnetic anisotropy, and spin-orbit torques in TI/FM heterostructures.

Findings

Enhanced Gilbert damping in highly crystalline Bi2Te3 films.

Observation of spontaneous exchange bias at low temperatures.

Disorder weakens exchange interactions at the interface.

Abstract

Thin films of Topological insulators (TIs) coupled with ferromagnets (FMs) are excellent candidates for energy-efficient spintronics devices. Here, the effect of crystalline structural disorder of TI on interfacial and magnetic properties of sputter-deposited TI/FM, Bi2Te3/Ni80Fe20, heterostructures is reported. Ni and a smaller amount of Fe from Py was found to diffuse across the interface and react with Bi2Te3. For highly crystalline c-axis oriented Bi2Te3 films, a giant enhancement in Gilbert damping is observed, accompanied by an effective out-of-plane magnetic anisotropy and enhanced damping-like spin-orbit torque (DL-SOT), possibly due to the topological surface states (TSS) of Bi2Te3. Furthermore, a spontaneous exchange bias is observed in hysteresis loop measurements at low temperatures. This is because of an antiferromagnetic topological interfacial layer formed by reaction of the diffused Ni with Bi2Te3 which couples with the FM, Ni80Fe20. For increasing disorder of Bi2Te3, a significant weakening of exchange interaction in the AFM interfacial layer is found. These experimental results Abstract length is one paragraph.