Ab initio study of electronic, mechanical, magnetic, and thermoelectric characteristics of Na2Nb(Cl/Br)6 for Spintronic and energy applications

Abstract

Spintronics is an emerging technology exploiting the spin degree of freedom of electrons, in which the spin functionality of electrons controls the multifunctional tasks of quantum-level devices. This article elaborates on the electronic, magnetic, mechanical, and thermodynamic aspects of double perovskite halides Na2Nb(Cl/Br)6 by Wien2k and Boltz Trap codes. The negative formation energy and higher energy release in ferromagnetic (FM) states than in antiferromagnetic (AFM) and paramagnetic (PM) states favor the stability of FM states. The tolerance factor (0.95, 0.98) has also been reported to ensure structural stability. The elastic constants confirm the Born mechanical stability criteria, ductile nature, large Debye and melting temperatures. Heisenberg's and Monte Carlo simulation calculations show that Curie's temperature is higher than room temperature. The band structures and magnetic moment illustrate half-metallic ferromagnetism with 100 % spin polarization. Furthermore, the density of states, p-d states hybridization, exchange constants, and exchange energies are elaborated to explore ferromagnetism. The distribution of magnetic moments in nonmagnetic sides specifies the role of 4d electrons of Nb in ferromagnetism. Furthermore, the power factor and the Figure of merit (0.65, 0.51) explain the effect of thermal conductivity and transport factors on the spin of electrons and thermoelectric performance. The Figure of merit and specific heat capacity increase their potential for thermoelectric energy harvesting applications.