A study of the magnetic, thermal, and optical absorption properties in Ho(OH)3 crystal

Abstract

This paper reports the result of our experimental study on the mean susceptibilities K̄ and also the molar anisotropies K∥–K⊥ between 300 and 80 K in pure Ho(OH)3 crystals. In our previous study we had shown that for Ho3+ compounds having C3h symmetry, the thermal variation of the magnetic anisotropies from 300–80 K are sensitively dependent on the detailed pattern of the crystal-field levels of the lowest 5I8 term, i.e., on the crystal-field parameters (CFP). Thus by fitting the experimental results of K̄, K∥–K⊥, K∥ and K⊥ K⊥ simultaneously in the temperature region studied, we determined the CFP for Ho(OH)3 more accurately than was possible from an analysis of spectral data which are not very informative in this crystal. We obtained B02 = 200 cm−1, B04 = −57 cm−1, B06 = −40 cm−1, and B66 = 400 cm−1. The values of B02 and B06 differed from the corresponding values for the dilute crystal, i.e., Ho3+:Y(OH)3, as reported from spectral studies. A similar type of difference in the values of CFP for dilute and pure Tb(OH)3 had also been reported earlier from spectral studies by Scott. The crystal field components of 5I8→5I4 transition in Ho(OH)3 are matched using our values of CFP. Using the crystal-field levels as obtained by us, we have shown here that the calculated values for saturated magnetization Msat, g values, and the Curie constant λ, are quite close to the observed values. From an analysis of each of the components of the total specific heat CT between 16–0.6 K, we have also shown that the magnetic specific heat has the functional behavior CM/R = (2.8±0.2)/T2, which is nearly the same as in the dilute system. The magnetic entropy SM was also calculated, and its thermal variation suggested that Ho(OH)3 behaves as a spin half system around liquid-helium temperatures but as temperature rises the contributions of the close-lying excited levels become effective and so Ho(OH)3 canot be treated as spin half system at such temperatures.