Density Functional Theory Study on the Thermo-elastic and Magneto-electronic Properties of Double Perovskite Oxides Sr2MNbO6 (M = V, Cr)

Double perovskite oxides have attracted much attention in material science and spintronic applications due to their exceptional physical properties. In this paper, the transition-metal double perovskite oxides Sr2MNbO6(M = V, Cr) are studied to investigate the effect of the magnetic cation M, using the full-potential linearized augmented plane wave method (FP-LAPW) within a generalized gradient approximation (GGA), Hubbard correction (GGA + U), and exact exchange for correlated electrons (EECE) in the framework of the density functional theory (DFT). The cubic phase is the most stable polymorph in the ambient condition for both double perovskites. The lattice parameters, interne coordinates, are in agreement with previous measurements and theoretical calculations. Furthermore, both of the examined materials are brittle in nature and have an elastically anisotropic character. More importantly, for Sr2VNbO6, a half-metallic ferromagnetism is predicted with a narrow band gap in the minority spin, whereas Sr2CrNbO6 shows a ferromagnetic insulator nature, and the estimated Curie temperatures are higher than the room temperature. We deduce that the M3+ (3dn-t2gn;S=n2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{t}}_{2g}^{n};S=\frac{n}{2}$$\end{document}) ions (n = 2or 3) have a significant effect on the magnetic moment and the electronic conducting, on the contrary to the nonmagnetic Nb5+ (4 d0-t2g0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{t}}_{2g}^{0}$$\end{document}) ions. The thermodynamic properties are predicted in the temperature range from 0.0 to 1000 K where the quasi-harmonic model remains fully valid. These results indicate that Sr2MNbO6 might have an important potential application in spintronic devices.