Paramagnetische Spin-Gitter- und Kreuzrelaxation in CeCl₃ · 7H₂O bei Temperaturen zwischen 1,1 und 4,2 °K

Abstract

The paramagnetic relaxation in single crystals of CeCl₃ · 7H₂O has been studied by the dispersion-absorption method at temperatures between 1.1 and 4.2 ‡K in magnetic fields up toH=13.5 kOe. Alternating magnetic fields with frequencies between 10 c/s and 10 kc/s, 50 kc/s and 110 kc/s, and a frequency of 24.3 mc/s have been used. At seven harmonic fields crossrelaxation processes are observed. They are explained by assuming that the Cerium-ions are coupled to form isolated pairs by an isotropic and antiferromagnetic interaction, and that the observed processes occur between certain numbers of pairs. For the energy splitting between the lower singlet and the upper triplet pair-states a value ofδE=k(1.16±0.05) ‡K is derived. The crossrelaxation times are temperature independent. They show a resonancelike dependence on magnetic field and increase exponentially with the number (1 to 5) of pairs participating in the single process. The spin-lattice relaxation is dominated by Raman-processes at temperaturesT>3 ‡K and at lower temperatures probably by inverse Orbach-processes of the pairs. — The results are discussed in terms of a theory given bySauermann andSchwegler.