THE ELECTRON SPIN RESONANCE OF VO2+ IONS IN TWO TYPES OF ALUMINIUM ALUMS

Abstract

The electron spin resonance spectrum of the vanadyl ion VO2+ is studied in single crystals of RbAl(SO4)2.12 H2O and CsAl(SO4)2.12 H2O, at room temperature and in the 9.2 kMc/s microwave frequency range. In RbAl(SO4)2.12 H2O the V–O axes are found to have three orientations directed along the cubic crystallographic axes, giving rise to three magnetic complexes. The spin Hamiltonian parameters are S = 1/2, [Formula: see text], [Formula: see text], [Formula: see text] cm−1, and [Formula: see text] cm−1. In CsAl(SO4)2.12 H2O the V–O axes are displaced from the crystallographic axes, giving rise to 12 magnetic complexes. The spin Hamiltonian parameters are S = 1/2, [Formula: see text], [Formula: see text], [Formula: see text] cm−1, and [Formula: see text] cm−1. The observed spectra are attributed to a vanadyl pentahydrate complex (VO2+.5 H2O) associated with a water-molecule vacancy.