Electrical and structural properties of pure and dysprosium doped $N{a}_{0.5}B{i}_{0.5}Ti{O}_3$ system: DFT and Monte Carlo simulation

Abstract

The chemical ordering, electrical, optical, and magnetic properties of $N{a}_{0.5}B{i}_{0.5}Ti{O}_3$ (NBT) and 25$\%$ dysprosium doped NBT (DyNBT) were investigated in the framework of first-principles calculations using the full potential linearized augmented plane wave (FP-LAPW) method based on spin-polarized density functional theory implemented in the WIEN2k code. We demonstrated that NBT structure is stable in the 001 A-site configuration, while DyNBT presents an A-site disorder perceived by the minimal energy difference between the different A-site configurations. A significant magnetic moment of $5\mu B$ emerges in DyNBT system, while NBT is known to be non-magnetic. Dysprosium in NBT matrix seems to form an ionic bonding with oxygen atoms whereas Bi-O forms covalent bonding which is responsible for the decrease of the polarization value from 42.3 $\mu C/c{m}^2$ for NBT to 22.08 $\mu C/c{m}^2$ for the doped compound. In the second part, the transition temperature and the hysteresis loops of $N{a}_{0.5}(B{i}_{1-x}D{y}_x{)}_{0.5}Ti{O}_3$ system x = 0 - $25\%$ were investigated using the Monte Carlo simulation. We observed a decrease in the transition temperature as a function of dysprosium introduction. We pointed out from the hysteresis loops, an apparent decrease of the coercive field together with the remanent polarization as a function of doping and also as a function of temperature. Our proposed model was seen to approach the values of experimental studies.