ELECTRON PARAMAGNETIC RESONANCE OF Ti3+ IONS IN TlAl(SO4)2∙12 H2O

Abstract

The paramagnetic resonance spectrum of Ti3+ ions in thallium alum (TlAl(SO4)2∙12 H2O) single crystals has been studied in the {100} planes at 4.2 °K with an X-band microwave spectrometer. The spectrum is an analogue of that reported by Dionne for Ti3+ ions in rubidium alum (RbAl(SO4)2∙12 H2O), but differs in that the lines occur at lower values of the magnetic field, and that no superhyperfine splitting was observed. As in the case of Rb alum, the spectrum was explained by considering a model of 12 magnetic complexes, the complexes being related to each other through the symmetry elements of the [Formula: see text] point group of the alum lattice. The three g factors for the spin Hamiltonian with [Formula: see text] were found to be 1.938, 1.834, and 1.790—within an accuracy of ± 0.005. The three different g factors were taken as evidence for a crystal electric field of orthorhombic symmetry. The orbital energy-level splittings required to give the observed g factors were calculated by a degenerate perturbation method. Since the crystals were colorless and since no value for 10 Dq is available in the literature, a unique set of splitting parameters could not be obtained. By giving the spin-orbit coupling constant λ values between 150 and 110 cm−1, a range of crystal-field energy-level splittings was determined, all of which predict that the cubic splitting 10 Dq is in the ultraviolet region of the frequency spectrum.