ELECTRON SPIN RESONANCE OF VO2+ IONS IN (NH4)2ZN2(SO4)3

The electron spin resonance spectrum of the vanadyl ion (VO2+) is studied in single crystals of (NH4)2Zn2(SO4)3, at room temperature and in the 9.4 KMc/s microwave frequency range. The V-O axes are found to have four possible orientations giving rise to four magnetic complexes. The V-O axes of two magnetic complexes lies in the (110) plane while the axes of the other two complexes lies in the plane perpendicular to (110). The populations in the four possible orientations are in the ratio 4:1:4:1. The complexes with the identical populations are equivalent but for the change in the relative directions of their axes, and hence the four magnetic complexes form into two groups. Futhermore, the vanadyl hyperfine lines show an additional anisotropic structure of five lines which is apparently lines show an additional anisotropic structure of five lines which is apparently due to the superhyperfine interaction of the unpaired spins of the transition metal ion, with some of the protons of the surrounding (NH4)+ molecules. All the spectra have been analysed using the spin-Hamiltonian corresponding to rhombic symmetry and the spin-Hamiltonian parameters are presented. © 1969, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.