Role of p-d hybridization in structural transition and magnetic properties of Co-substituted Mn3O4: X-ray absorption spectroscopy study

This work investigates the role of p-d orbital hybridization in the structural transition from tetragonal I41/amd to cubic Fd3̅m and enhancement in Néel temperature (TN) from 43 K to 175 K in (Mn1−xCox)3O4 (where x = 0.0, 0.1, 0.2, 0.3, 0.5, and 0.6). X-ray absorption spectra of Co-L2,3 and Mn-L2,3 edges show that the high-spin Co2+ cations initially substitute the Mn2+ at the tetrahedral-sites. When the tetrahedral-sites are fully occupied, then the high-spin Co3+ cations begin to occupy the octahedral-site. The substitution of Co cations at both the tetrahedral and octahedral-sites increases the bond angle between adjacent tetrahedral and octahedral site cations via O-2p orbitals, suppressing the orbital instability of Mn3+ cations. These effects dramatically enhance the superexchange interaction and hence the TN.