Defect Engineered Room-Temperature Ferromagnetism in Quasi-Two-Dimensional Nitrided CoTa2O6

TL;DR

This study demonstrates that defect engineering via thermal ammonolysis induces room-temperature ferromagnetism in quasi-2D CoTa2O6, supported by experimental and first-principles analyses, and predicts a pressure-induced phase transition.

Contribution

It introduces a novel defect engineering approach to achieve room-temperature ferromagnetism in quasi-2D CoTa2O6 and elucidates its origin through first-principles calculations.

Findings

Induced ferromagnetism above room temperature in CoTa2O6.

Identified specific CoON defect configuration responsible for ferromagnetism.

Predicted pressure-induced insulator-to-metal transition at 24.5 GPa.

Abstract

Thermal ammonolysis of quasi-two-dimensional (quasi-2D) CoTa2O6 yields the O2-/N3- and anionic vacancy ordered Co2+Ta5+2O6-xN2x/3$\Box$x/3 (x $\leq$ 0.15) that exhibits a transition from antiferromagnetism to defect engineered above room-temperature ferromagnetism as evidenced by diffraction, spectroscopic and magnetic characterizations. First-principles calculations reveal the origin of ferromagnetism is a particular CoON configuration with N located at Wyckoff position 8j, which breaks mirror symmetry about ab plane. A pressure-induced electronic phase transition is also predicted at around 24.5 GPa, accompanied by insulator-to-metal transition and magnetic moment vanishing.