Host-lattice systematics of EPR spectra of Mn2+-doped isomorphic metal hexakisantipyrine perchlorate and EPR of Cu2+ in copper pentakisantipyrine perchlorate

Abstract

X-band EPR measurements on Mn2+-doped single crystals of isomorphous metal hexakisantipyrine perchlorate (metal=Ca, Cd, Mg, Co, and Pb) have been performed. For the case of calcium and cadmium metal hosts, the measurements were made from room temperature down to liquid helium temperature, while for the remaining metal hosts the measurements were made only at room temperature. The spin Hamiltonian parameters are rigorously evaluated using a least-squares fitting computer technique, especially adapted to electron-nuclear spin coupled systems. As for the systematics of the spin Hamiltonian parameters, at room temperature the variation of the zero field splitting parameters b02 and b04 is found to be approximately linear in the host metal ion radius. In order to estimate the Cu2+–Mn2+ exchange interaction, 5%–50% of Ca2+ ions in Mn2+-doped calcium hexakisantipyrine perchlorate were substituted for by Cu2+, and the EPR spectra were recorded from room temperature down to liquid helium temperature. However, even at liquid helium temperature, the presence of the paramagnetic ion Cu2+ in this host caused no significant change of the g value for Mn2+ as compared with that in the pure diamagnetic host indicating negligible Cu2+–Mn2+ exhange constant. EPR measurements on Cu2+ in copper pentakisantipyrine perchlorate were also made at room, liquid nitrogen, and liquid helium temperatures and the principal values and direction cosines of the principal axes of the g and A tensors were estimated, using a rigorous least-squares fitting procedure.