Soft X-ray synchrotron radiation spectroscopy study of the Co0.6Fe0.9Mn1.5O4 spinel with nano-checkerboard patterns

Abstract

The electronic structures of water-quenched (WQ) and checkerboard (CB) samples of spinel Co0.6Fe0.9Mn1.5O4 have been investigated by employing soft X-ray absorption spectroscopy and soft X-ray magnetic circular dichroism. The valence states of Co, Fe, and Mn ions are found to be nearly divalent (Co2+), trivalent (Fe3+), and Mn2+-Mn3+ mixed-valent, respectively, in both WQ and CB Co0.6Fe0.9Mn1.5O4. Mn2+ and Mn3+ ions occupy the tetrahedral (T d ) and the octahedral (O h ) sites, respectively, with their spin magnetic moments antiparallel to each other while Fe3+ and Co2+ ions occupy both O h and T d sites. As the CB nano-structures are formed in Co0.6Fe0.9Mn1.5O4, some of the T d -site Mn2+ ions transform to O h -site Mn3+ ions while some of the O h -site Fe3+ ions transform to T d -site Fe3+ ions. These findings indicate that the chemical phase separation in the CB nano-structures is mediated by the cooperative distortions of Janh-Teller Mn3+ ions.