High-resolution67Zn-Mössbauer study of oxide spinels

We report on first experiments to investigate the electronic structure in the normal spinels ZnAl₂O₄ and ZnFe₂O₄ and in the inverse spinels Zn₂SnO₄ and Zn₂TiO₄ using the high-resolution⁶⁷Zn-Mössbauer spectroscopy. The electric field gradient for⁶⁷Zn at the B (octahedral) site in ZnAl₂O₄ is negative, whereas the A (tetrahedral) site remains essentially cubic, however, with a more positive center shift. ZnFe₂O₄ orders antiferromagnetically at ≈10K. Due to superexchange a magnetic field is observed at⁶⁷Zn. In the inverse spinels short range order leads to only few (Zn,Sn) and (Zn,Ti) configurations at the octahedral sites. The s-electron densities at the⁶⁷Zn sites are distinct and cover a surprisingly broad range for Zn₂TiO₄. This strongly suggests that d-electrons of Ti play an essential role in the chemical bond of this compound.