Electrical and structural properties of pure and dysprosium doped $Na_{0.5}Bi_{0.5}TiO_{3}$ system: DFT and Monte Carlo simulation

TL;DR

This study combines first-principles calculations and Monte Carlo simulations to explore how dysprosium doping affects the structural, electrical, and magnetic properties of Na0.5Bi0.5TiO3, revealing magnetic moments, reduced polarization, and lowered transition temperatures.

Contribution

It provides new insights into the effects of dysprosium doping on NBT's properties using combined DFT and Monte Carlo methods, which was not previously studied.

Findings

Dy doping induces magnetic moments in NBT.

Dysprosium reduces polarization and transition temperature.

Doping decreases coercive field and remanent polarization.

Abstract

The chemical ordering, electrical, optical, and magnetic properties of $Na_{0.5}Bi_{0.5}TiO_{3}$ (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 ${\mu}C/cm^{2}$ for NBT to 22.08 ${\mu}C/cm^{2}$ for the doped compound. In the second part, the transition temperature and the hysteresis loops of $Na_{0.5}(Bi_{1-x}Dy_{x})_{0.5}TiO_{3}$ 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.