Impact of 3d-transition metal [T = Sc, Ti, V, Cr, Mn, Fe, Co] on praseodymium perovskites PrTO₃: standard spin-polarized GGA and GGA+U investigations

Abstract

Generalized gradient approximation (GGA) computations based on the first-principles density functional theory (DFT) are executed to gain insight into the structural stability and physical properties of the 3d-transition-metal-based praseodymium series of perovskite compounds PrTO₃. Correspondingly, to investigate the effect of on-site Coulomb repulsion energy, the exchange-correlation version of GGA is implemented via utilizing the (GGA+U) functional. The computed ground state energies ($E_{0}$) and equilibrium structural parameters of the varied T-site [T = Sc, Ti, V, Cr, Mn, Fe, Co] in the unit cell of PrTO₃ reveal a cubic symmetry (Pm-3m) in all compounds, in a good match with the few existing DFT and experimental literature. Besides, the computed spin-polarized band structures and partial and total density of states (DOS) within GGA predict a half-metallic (HM) behaviour for [T = Sc] perovskite and a metallic nature for the rest [T = Ti, V, Cr, Mn, Fe, Co]. The analysis of $E_{0}$ results, DOSs and spin magnetic moments indicates that all perovskites PrTO₃ are stable in a ferromagnetic (FM) phase via the double exchange interaction T³⁺–O^2-–T⁴⁺. PrTO₃ show FM order with fractional values of their total spin magnetic moment per unit cell ($M_{{{\text{PrTO}}_{3} }}$), except [T = Sc] perovskite that gives integer value ($M_{{{\text{PrScO}}_{3} }}$ ≈ 2.0 $\mu_{{\text{B}}}$) with HM-FM property. Conversely, it is found that PrTO₃ exhibit HM-FM properties when [T = Sc, V, Cr, Mn, Fe] plus GGA+U is applied. Due to the cation–anion hybridizations, Pr³⁺–O^2– and T³⁺–O^2–, both Pr³⁺ and T³⁺ ions contribute to the largest part of $M_{{{\text{PrTO}}_{3} }}$ with minor effects coming from O^2– ions and interstitials. Furthermore, the three-dimensional and two-dimensional electronic charge density plots of PrTO₃ along the (110) plane confirm strong ionic nature along the Pr³⁺–O^2– bonds, whereas the other O^2––T³⁺–O^2– bonds have strong covalent character.