Electron paramagnetic resonance studies of VO²⁺ in KNO₃ and CsNO₃ single crystals

Abstract

The electron paramagnetic resonance spectra of the VO²⁺ ion doped in KNO₃ and CsNO₃ single crystals have been investigated over a wide temperature range. Room-temperature studies reveal that there is a very fast readjustment of VO²⁺ ion, in both crystals, which is manifested in the presence of a single isotropic octet, thereby exhibiting a low viscous "liquidlike" nature. At low temperatures an anisotropic spectrum is obtained due to the hindered rotation of the VO²⁺ ion. The effect of CsNO₃ in hindering the rotation of a vanadyl ion is found to be greater than that of KNO₃. The linewidths at room temperature are found to depend upon the mI quantum number, and an attempt is made to fit the linewidth data of the present study in the theoretical expressions of Kivelson. It is found that Kivelson's theory can qualitatively explain the observed variation of linewidth with nuclear quantum number m_I, but the experimental data could not be fit quantitatively into the theory. All the spectra are analyzed using the usual spin-Hamiltonian method.