Bulk Intergrowth of a Topological Insulator with a Room Temperature Ferromagnet

TL;DR

This paper reports the synthesis of bulk composite crystals combining a room temperature ferromagnet, Fe7Se8, with a topological insulator, Bi2Se3, maintaining their intrinsic properties and demonstrating potential for spintronic applications.

Contribution

It introduces a method to create crystallographically oriented bulk intergrowth crystals of Fe7Se8 and Bi2Se3, preserving their individual bulk properties.

Findings

Fe7Se8 and Bi2Se3 form micron-scale, oriented intergrowth crystals.

The intergrowth retains the ferromagnetic and topological surface states.

The properties of each phase are preserved in the composite.

Abstract

We demonstrate that the layered room temperature ferromagnet Fe7Se8 and the topological insulator Bi2Se3 form crystallographically oriented bulk composite intergrowth crystals. The morphology of the intergrowth in real space and reciprocal space is described. Critically, the basal planes of Bi2Se3 and Fe7Se8 are parallel and hence the good cleavage inherent in the bulk phases is retained. The intergrowth is on the micron scale. Both phases in the intergrowth crystals display their intrinsic bulk properties: the ferromagnetism of the Fe7Se8 is anisotropic, with magnetization easy axis in the plane of the crystals, and ARPES characterization shows that the topological surface states remain present on the Bi2Se3. Analogous behavior is found for what has been called "Fe-doped Bi2Se3."