Spin-Lattice Relaxation of Cr^<3+> in Coexistence with Ti^<3+> in Al_2O_3

概要

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The shortening of spin-lattice relaxation time caused by a second spin having a fast spin-lattice relaxation is studied. In ruby (Cr; Al_2O_3) containing about 0.02% of Ti^<8+> as an additional impurity, a change of spin-lattice relaxation times of Cr^<3+> has been observed with a variation of paramagnetic concentrations and the frequency difference between Cr^<8+> and Ti^<8+> resonance transitions, at liquid helium temperatures and using the decay method. Experimental results are compared with the predictions of rate equations. At a crossing of the resonance lines of Cr^<8+> and Ti^<8+>, the relaxation time of Cr^<8+> for specimens having about 0.1% of Cr can be reasonably described by the rate equations. For 0.02% Cr, simultaneous flip-flop between Cr^<8+> and Ti^<3+> becomes a slow process. In absence of the crossing, the relaxation is also found to be accelerated by the presence of Ti^<3+>.
社団法人日本物理学会の論文
1965-08-05