A Mössbauer Study of Fe57 in Distorting Spinels

The effect of cooperative John-Teller distortion on Mossbauer absorption spectra in the paramagnetic state of germanium-substituted copper ferrite was measured. The measurements at 430 and 510 deg C show almost the same spectra consisting of two absorption lines with isomer shifts of 0.17 and 0.11 mm/sec, and quadrupole splittings of 0.50 and 0.50 mm/sec, respectively. No appreciable change of the quadrupole splitting is present in a cubic phase and in a tetragonal phase. In the ferromagnetic state, directions of spins are uniform in a domain, but those of the electric field gradients at Fe/sup 57/ nuclei on octahedral sites take four equivalent (111) directions in a unit cell, and so the angular part of the quadrupole interaction is not unique. (C.E.S.)