Electronic and magnetic properties of CoFe2O4 nanostructures: An ab-initio and Monte Carlo study

Abstract

Sub-magnetic ordering of CoFe2O4 spinel was elaborated through the electronic structure via ab-initio calculations. PBE-GGA was preferred to obtain band structure and density of states applying Hubbard correction. Considered magnetic states, including distinctive sub-orders, exhibited several band gaps and magnetic features. Applying the magnetic force theorem to the ground state solution, exchange coupling energies were obtained. We double-checked O(p)-Fe/Co(d) hybridizations and exchange energies of considered magnetic states contributing to FM/FiM phases. Co–O hybridizations were stronger than Fe–O. Rest couples, obviously overshadowed the contribution of oxygen-connected ions, herewith, assuring different strengths of exchange energy. Initially, FM coupled Co–Co and Fe–Fe pairs had the strongest values. Magnetocrystalline anisotropy had close-set values consistent with previous studies (0.09210385eV for Co–Co, AFM, and Fe–Fe, FM). Curie temperatures (Tc) were obtained from temperature-dependent normalized magnetization and magnetic susceptibility curves using the Monte Carlo method on a classical Heisenberg model. Exchange energies, magnetocrystalline anisotropy, and magnetic moments obtained from DFT calculations were implemented as inputs to the simulation process. The highest Tc was found to be 725 K for the FM sub-order state. Other states undergo a phase transition under 500 K and 445 K temperatures, respectively. Considered magnetic orders can occur concerning experimental conditions and production method/procedure of CoFe2O4 spinel ferrites.