The thermal and magnetic properties of ytterbium ethyl sulphate between 20°k and 1°k

The susceptibility of a single crystal of ytterbium ethyl sulphate has been measured between 20°k and 1°k, Below 4°k the results obeyed the relations Xπ = 1.08/T per mol, and X⊊ =0.0615 per mol. These measurements served to identify the ground doublet state of the ytterbium ion in this case as |J= 7/2 , J5= ± 8/2 >. The magnetic specific heat was measured at five temperatures between 3°k and 1°k by the relaxation method. The results were given by CT2/R=4.34 × 10−4, in agreement with calculations based on dipole-dipole and hyperfine interactions alone. The spin lattice relaxation time τ was also measured. At 3°k, τ ≃5 × 10−4 sec and was very temperature dependent. Susceptibility measurements above 4°k indicated the population of excited states, which could not be unambiguously identified. Their separation from the ground state was at least 57°k.