Emergent magnetic states and tunable exchange bias at all 3d nitride heterointerfaces

TL;DR

This study demonstrates the fabrication of high-quality Fe3N nitride films with tunable magnetic properties and exchange bias at heterointerfaces, revealing thickness-dependent magnetic transitions and strain-induced magnetic state control.

Contribution

It reports the synthesis of single-crystalline Fe3N films with controlled thickness and explores their magnetic and electronic properties, including emergent exchange bias influenced by lattice deformation.

Findings

Ferromagnetism persists in Fe3N films down to 8 Å thickness.

Exchange bias at Fe3N/CrN interfaces can be tuned by bending curvature.

Magnetization and electronic states are highly sensitive to film thickness.

Abstract

Interfacial magnetism stimulates the discovery of giant magnetoresistance and spin-orbital coupling across the heterointerfaces, facilitating the intimate correlation between spin transport and complex magnetic structures. Over decades, functional heterointerfaces composed of nitrides are seldomly explored due to the difficulty in synthesizing high-quality and correct composition nitride films. Here we report the fabrication of single-crystalline ferromagnetic Fe3N thin films with precisely controlled thickness. As film thickness decreasing, the magnetization deteriorates dramatically, and electronic state transits from metallic to insulating. Strikingly, the high-temperature ferromagnetism maintains in a Fe3N layer with a thickness down to 2 u. c. (~ 8 {\AA}). The magnetoresistance exhibits a strong in-plane anisotropy and meanwhile the anomalous Hall resistance reserves its sign when Fe3N layer thickness exceeds 5 u. c. Furthermore, we observe a sizable exchange bias at the interfaces between a ferromagnetic Fe3N and an antiferromagnetic CrN. The exchange bias field and saturation moment strongly depend on the controllable bending curvature using cylinder diameter engineering (CDE) technique, implying the tunable magnetic states under lattice deformation. This work provides a guideline for exploring functional nitride films and applying their interfacial phenomena for innovative perspectives towards the practical applications.