Prospect of increasing the Néel temperature of Cr₂O₃ using 4d and 5d transition metal defects

Magnetoelectric antiferromagnet Cr₂O₃ is a promising material for spintronic applications. For practical purposes it is desirable to enhance its Néel temperature (308K). Here we employed first-principles methods to investigate the potential enhancement of its Néel temperature through doping of 4d and 5d transition metal impurities (Mo, W, Nb, Ta, Zr, and Hf). Hybrid functional calculations are performed, and the defects are simulated using the supercell method. The effect of doping on Néel temperature is assessed by calculating the total energy change when the local moment on a transition metal impurity or on the nearby Cr atoms is flipped. The likelihood of incorporating these defects is investigated through formation energy calculations. Our study identifies isovalent Mo and W defects as the promising candidates to increase the Neel temperature, and this enhancement is found to be assisted by the enhanced of direct exchange mediated by the impurity state. The possibility of experimental incorporation of these defects and their predominant charge state will be discussed.