Exchange Coupling in Synthetic Anion-Engineered Chromia Heterostructures

Control of magnetic states by external factors has garnered a mainstream status in spintronic research for designing low power consumption and fast-response information storage and processing devices. Previously, magnetic-cation substitution was the conventional approach to induce ferromagnetism in an intrinsic antiferromagnet. Theoretically, anion doping is proposed to be another means to change magnetic ground states. Here, the authors demonstrate the synthesis of high-quality single-phase chromium oxynitride thin films using in-situ nitrogen doping. Unlike antiferromagnetic monoanionic chromium oxide and nitride phases, chromium oxynitride exhibits a robust ferromagnetic and insulating state, as demonstrated by the combination of multiple magnetization probes and theoretical calculations. With increasing the nitrogen content, the crystal structure of chromium oxynitride transits from trigonal (R3 over bar c) to tetragonal (4 mm) phase and its saturation magnetization reduces significantly. Furthermore, they achieve a large and controllable exchange bias field in the chromia heterostructures by synthetic anion engineering. This work reflects the anion engineering in functional oxides towards potential applications in giant magnetoresistance and tunnelling junctions of modern magnetic sensors and read heads.

Automated summary

This study demonstrates the synthesis of high-quality single-phase chromium oxynitride thin films using in-situ nitrogen doping, which exhibits robust ferromagnetic and insulating state. By increasing nitrogen content, the crystal structure changes and saturation magnetization decreases significantly. The authors also achieve a large and controllable exchange bias field in the chromia heterostructures through synthetic anion engineering, reflecting potential applications in modern magnetic sensors and read heads.