Magnetic complexity, magnetodielectric effect and DFT calculations on correlation driven Gd2CoMnO6 insulator

Abstract

In the family of Re<inf>2</inf>CoMnO<inf>6</inf> manganite double perovskites, in contrast to parent La<inf>2</inf>CoMnO<inf>6</inf> compound, Gd<inf>2</inf>CoMnO<inf>6</inf> exhibits multiple magnetic transitions; ferromagnetic (FM) ordering, T<inf>C</inf> ∼ 112 K followed by AFM transition, T<inf>N</inf> ∼ 47 K, Gd spins ordering for T < 10 K and large isothermal entropy changes. A study of DC field-superimposed AC magnetic susceptibility measurements revealed the field-induced magnetic glassy behavior below T<inf>C</inf> and enhancement of FM correlations above T<inf>C</inf>. From the analysis of Almeida-Thouless behavior and dynamical power-law fit to frequency dependent AC susceptibility, Gd<inf>2</inf>CoMnO<inf>6</inf> exhibits a volume spin glass-like nature below the freezing temperature, T<inf>f</inf> ∼ 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. 114 194,102 (2013)) confirms the spin-phonon coupling induced magnetodielectric effect. Further, the ground-state electronic structure and magnetic properties of Gd<inf>2</inf>CoMnO<inf>6</inf> are investigated using DFT + U formalism with Vienna Ab-initio Simulation Package (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 U<inf>eff</inf> ≥ 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. © 2022