Crystal-Field Effects and the Anisotropic Magnetization of TmSb

We show that the experimental results for the susceptibility and high-field anisotropic magnetization of TmSb can be understood on the basis of crystal-field effects. The absence of any exchange effects is verified by experiments on Tm0.53{Y}0.47$Sb giving the same susceptibility and high-field anisotropic magnetization per Tm ion as in TmSb. The theory and calculation of the anisotropic magnetization are described, and the use of such measurements to determine crystal-field parameters is discussed. Such anisotropic magnetization experiments are particularly valuable in determining the relative importance of fourth- and sixth-order contributions to the crystal field. Analysis of the present susceptibility and high-field magnetization experiments shows that the crystal field is predominantly fourth order, and gives an energy splitting of 26.6^∘{}K from the Γ₁ singlet ground state to the Γ₄ triplet first excited state of Tm³⁺ in TmSb.