Electron spin-lattice relaxation of Cu ++ in zinc ammonium tutton salt

Abstract

Electron spin-lattice relaxation rates of Cu ++ in Zn(NH 4) 2(SO 4) 2·6H 2O have been measured as a function of temperature and magnetic field. The measurements were carried out for four different concentrations of Cu ++ ions in the samples: 100%, 10%, 1.0% and 0.20%. At approximately 3000 Oe relaxation rates have been observed in the temperature range 1.2 < T < 15 K. At the lower temperatures relaxation rates proportional to T +1 and strongly dependent on the concentration of Cu ++ in the samples have been measured. At the higher temperatures a T 9 dependence has been observed. The relaxation rates in the He temperature range proved to be extremely low. At 2.25 K relaxation rates at non-resonant fields could be measured for 200 < H < 6000 Oe. At the higher fields a H 4 dependence independent on concentration has been observed. At the lower fields a H -1 dependence, strongly influenced by the concentration of Cu ++ occurs. The observed temperature and field dependence can be explained by Kronig-Van Vleck relaxation mechanisms and simultaneous relaxation via pairs of interacting Cu ++ ions.