A Comparative DFT Study of Structural, Electronic, Magnetic, and Optical Properties of Ferromagnetic and Paramagnetic Double Perovskites A2NdNbO6 (A = Ba, Sr) for Spintronic and Magnetic Sensor Applications

Abstract

The density functional theory has been used in this work to investigate the structural, magnetic, optical, and electronic properties of the double perovskite compounds Ba2NdNbO6 and Sr2NdNbO6. The magnetic stability of both compounds was verified, showing that they are stable in a ferromagnetic state with no phase transition to a paramagnetic state when they were exposed to external pressure. Structural properties, such as crystal constants, atomic positions, and bulk modulus, were calculated, and thermodynamic stability was verified at the most stable state and even under pressure up to 20 GPa. The equation-of-state fitting yields equilibrium lattice constants of 8.5465 & Aring; for Ba2NdNbO6 (FM) and 8.4166 & Aring; for Sr2NdNbO6 (FM), with corresponding bulk moduli of 145.13 GPa and 154.34 GPa, respectively. The semiconducting behavior of the studied compounds in both the up and down spin channels was verified, with energy gap values of 1.348 eV and 3.566 eV for Ba2NdNbO6, and 0.956 eV and 3.588 eV for Sr2NdNbO6, respectively. This makes the compounds suitable for several applications, such as spin filters, magnetic valves, smart magnetic switches, and magnetic field sensors. Magnetic stability has been verified under external pressure, where the total magnetic moment remained constant at 3 mu B for both compounds. Optical properties were investigated, showing that both compounds exhibit strong reflectivity in the spin-up state. These properties highlight the significance of these compounds for advanced scientific applications in spintronics, magnetic devices, and sensor technologies.