Understanding the structural behaviors and abrupt enhancement in magnetic ordering temperature of Fe-substituted Mn3O4

Abstract

We report an increase in magnetic ordering temperature from 43 K to 425 K and a structural phase transition from tetragonal I41/amd (x = 0.00) to cubic Fd3¯m (x = 0.40) in (Mn1-xFex)3O4 (x = 0.00–0.40) systems. The phase diagram clearly demonstrates that lattice constants a√2 and c converge smoothly with Fe-substitution and become equal for x = 0.40, while the room temperature magnetic moments increase from 0.15 μB/f.u. (x = 0.10) to 1.1 μB/f.u. (x = 0.40). There are two possible cationic distribution scenarios for Fe cations; one leads Fe2+ to occupy the tetrahedral site, while the other leads Fe3+ to occupy the octahedral site. The octahedral site preference energy indicates that Fe3+ cations occupying the octahedral site have higher preference values. X-ray absorption spectra studies of MnL2,3-edge and FeL2,3-edge confirm that Fe3+ cations occupy octahedral sites by replacing Jahn-Teller active Mn3+ cations. OK-edge spectra revealed that Jahn-Teller distortion is reduced in the cubic x = 0.40 system. However, the higher structural symmetry is not the most significant factor in the abrupt enhancement of magnetic ordering temperature. The increase in magnetic ordering temperature could be understood on the basis of increased spin moment coupling between tetrahedral and octahedral cations due to substitution of Fe3+ cations at the octahedral site.