J[formula omitted] Mott-insulating to S = 0 metal transition in Ce@Y-doped Y[formula omitted]NiIrO[formula omitted]

Abstract

Double perovskite oxides (DPOs) having 3d-5d electrons provide an optimal field to investigate the entanglement between spin–orbit coupling and electron correlation, displaying unusual physical phenomena. Here, we predicted a large magnetic anisotropy energy (MAE) constant of 1.7 × 108 erg/cm3 in a pristine ferrimagnetic (FiM) Y2NiIrO6 DPO with the magnetic easy axis of the monoclinic b-axis. The estimated Curie temperature (TC) of 198 K using the Heisenberg model agrees well with the experimentally observed value of 192 K. Antiferromagnetic coupling between Ni and Ir ions is confirmed, which supports the FiM as a ground state of the system. Furthermore, it is found that the motif displays a Mott-insulating nature because of the exceptional Jeff=12 state of Ir+4 with an effective magnetic moment (meff.) of ∼2.19μB/u.c. (per unit cell), where Ni/Ir ion contains 1.68/−0.49μB. Upon substitution of Ce at Y-site (Ce@Y), few states grow at the Fermi level which belongs to Ir 5d orbitals and meff. enhanced to 3.13 μB/u.c., while FiM survives as a ground state. Along with this, Ni moment remains unchanged, while it substantially reduces to −0.10μB for Ir ion which leads to be in a ＋ 3 (5d6) state with S = 0 and almost persists in the paramagnetic phase. Due to the larger atomic radii of Ce than that of Y, the Ce@Y-doped motif exhibits a large structural distortion as compared to the pristine one, which increases the MAE and TC values simultaneously. Furthermore, calculated enthalpies of formation, distinct elastic constants, and phonon dispersion spectrums ensure the thermodynamic, mechanical, and dynamical stability of the pristine as well as the Ce@Y-doped system, respectively.