Electronic structure calculation of the structural and magnetic properties of the MgFe2O4. From bulk to surface

MEDINA CHANDUVÍ H.H.; A.V. GIL REBAZA; A.M. MUDARRA NAVARRO; L.A. ERRICO

La Plata

Workshop; X Workshop on Novel Methods for Electronic Structure Calculations; 2023

In this work we present an ab initio study of the structural, electronic, magnetic, and hyperfine properties of Magnesium ferrite, MgFe2O4 (spinel structure). This study was carried out within the framework of Density Functional Theory (DFT) using the FP-LAPW+LO and Pseudopotential methods, employing the Generalized Gradient Approximation (GGA) and the GGA+U for the potential term and exchange. The calculations show that the equilibrium structure corresponds to an inverted and antiferromagnetic configuration, where the magnetic moments of the Fe atoms at A sites are ferromagnetically ordered among themselves and antiferromagnetically with respect to the Fe in the sub lattice of B sites, while the magnesium atoms do not polarize. The GGA calculations underestimate the energy gap of the system, while GGA+U predicts a gap of 2.4 eV, value that agrees with what has been reported experimentally [1], and a magnetic moment of Fe atoms of ±4.1 μB , a characteristic value for this type of compounds and in accordance with the experimental values reported in the literature [2]. The hyperfine parameters calculated at the Fe sites (isomer shift, quadrupole splitting and hyperfine field) are in excellent agreement withthose experimentally obtained by Mössbauer spectroscopy reported in the literature [3], supporting the equilibrium structure predicted by FP-LAPW+ LO. The surface of the MgFe2O4 ferrite was also studied, considering different terminations and considering structural reconstructions in all cases. The presented results predict that the most stable surface is inverted and exhibits a net magnetic moment, resulting in a ferrimagnetic system.