Paramagnetic relaxation of some iron group ions in magnesium oxide.

Electron spin-lattice relaxation rates have been investigated as a function of concentration and temperature between 1.8° and 4.2° Kelvin for cr3+, v2+, Mn2+, Co2+, and Ni2+ ions in MgO. Both pulse saturation and continuous saturation methods were used. A number of interesting aspects of the results are discussed. In at least some cases, the results are found to depend on the concentration of other impurities in the MgO lattice. A comparison is made with the relaxation rates predicted by theory. There are indications that for most of the samples studied, a relaxation process other than direct spin-lattice relaxation is dominant. Cross relaxation to the fast relaxing Fe2+ impurity is suggested as one such process. [...