Optical measurement of ultrashort spin-lattice relaxation time in the ground state of the thulium ion in cubic fields

Ultrashort spin-lattice relaxation times in the ground state of Tm2+ doped in CaF2 and SrF2 crystals are measured from the decay curves of the magneti zation, which is created and detected by optical pulses. The temperature de pendences of the spin-lattice relaxation rate 1/T-1 near room temperature a re deviated from the well-known T-9 dependence for the Raman process. The d eviation is explained consistently by a theory of the Raman process includi ng the Debye temperature of the host crystal. (C) 2000 Elsevier Science B.V . All rights reserved.