Paramagnetic Relaxation of Chromium Ion in Ruby and Potassium Alum

概要

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Measurements have been made of spin-lattice relaxation times T_1 of single Cr ion impurities in ruby and alum, using the decay method at liquid helium temperature. In ruby, T_1 is dependent on the Cr ion concentration C, for specimens having more than 0.01% Cr, whereas in alum T_1 is nearly independent of C. The difference between them is explained in terms of spin-lattice relaxation via exchange pairs. The relaxation time T_1 in ruby varies as C^<-1> between 0.044% and 0.28%, which agrees with the theoretical prediction. At higher concentrations, T_1 decreases more rapidly with C and its temperature dependence becomes faster than T^<-1>. In very dilute crystals, T_1 at 4.2°K is 200 msec and 3 msec in ruby and alum respectively. The comparison of the values of T_1 for both crystals is given on the basis of the Van Vleck mechanism, and it is shown that the orbit-lattice interaction between Cr and ligand ions is larger in ruby than in alum.
社団法人日本物理学会の論文
1964-12-05