Field dependence of spin-lattice relaxation of Nd3+ ions in Y3Al5O12 crystals |
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Authors: | L. K. Aminov I. N. Kurkin S. P. Kurzin D. A. Lukoyanov I. Kh. Salikhov R. M. Rakhmatullin |
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Affiliation: | (1) Kazan’ State University, 420008 Kazan’, Russia |
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Abstract: | Our studies involve measuring spin-lattice relaxation times for Nd3+ ions in yttrium-aluminum garnets over the temperature range 4–50 K at 9.25 and 36.4 GHz for different orientations of the external magnetic field in relation to the crystallographic axes. The temperature dependence of the relaxation rate is described by T 1 −1 =AT n+b exp(−Δ/kT), where n varies from sample to sample, with n=1 for “perfect” samples (i.e., with the longest relaxation times). Here Δ is approximately 130 cm−1, which is the energy of the excited Kramers doublet of the neodymium ion closest to the ground state, and this makes it possible to interpret the second term in T 1 −1 as the contribution of two-stage relaxation proceeding through the intermediate level Δ. A strong field dependence of these processes has been discovered: when the frequency was increased fourfold, the relaxation rate increased by a factor of 10. The effect is a specific manifestation of the degeneracy of the excited level, breaking of the symmetry of the crystalline field due to lattice defects, and the prevalence of deformations of a certain type in the spin-lattice interaction. Zh. éksp. Teor. Fiz. 111, 332–343 (January 1997) |
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