Magnetic Complexity, Magnetodielectric Effect and Dft Calculations on Correlation Driven Gd2comno6 Insulator

Abstract

ABSTRACTIn the family of Re 2 CoMnO 6 (Re= rare-earth) cobaltite-double perovskites, in contrast to the parent La 2 CoMnO 6 compound, Gd 2 CoMnO 6 exhibits multiple magnetic transitions; ferromagnetic (FM) ordering, T C ~112 K followed by AFM transition, T N ~47 K, Gd spins ordering for T<10 K and largeisothermal entropy changes. A study of DC field-superimposed AC susceptibility measurements revealed the field-induced magnetic glassy behavior below T C and enhancement of FM correlations above T C . From the analysis of Almeida-Thouless behavior and dynamical power-law fit to frequency dependent AC susceptibility, Gd 2 CoMnO 6 exhibits a volume spin glass-like nature below the freezing temperature, T f ~117.5 K. The isothermal field-dependent magnetic and dielectric permittivity data and temperature dependent Raman measurements (reported in ref. R. X. Silva et al ., J, Appl. Phys. 114 194102 (2013)) confirms the spin-phonon coupling induced magnetodielectric effect. Further, the ground-state electronic structure and magnetic properties of Gd 2 CoMnO 6 were investigated using DFT+U formalism with VASP code and predicted the material to be a correlation-driven insulator. The correlation value of the Hubbard U parameter at the 4f-Gd elements changes the stability of the magnetic state from Ferri to FM spin alignment for Ueff ≥ 3 eV and is correlated to the experimentally observed field-induced transformation of the short-range-order FiM/spin-glass-like phase into the long-range ordered FM phase.

Keywords: Double Perovskites, Spin-glass, Ferromagnetism, Magnetodielectric effect and DFT calculations