Terbium heat capacity

There have been attempts to calculate the spin wave contribution to the heat capacity from inelastic neutron scattering data for Tb and Gd (Sedaghat and Cracknell, 1971 Stevens and Krukewich, 1973). The former found the power of T to increase with increasing temperature for gadolinium from n = 1.56 to n = 2.3, but no simple power law above 14 K. The latter investigators found n 1.5 for terbium and gadolinium. Wells et al. (1974) have confirmed that for... 

Let us begin the discussion of terbium by looking at the nuclear contribution (table 5.2). Krusius et al. (1969) found a good fit with parameters very close to the NMR results from 0.03 to 0.5 K, at which temperature their heat capacity results joined onto those of Lounasmaa and Roach (1962). Their values agree within 1% with those of van Kempen et al. (1964). Thus we might safely assume Cn of Tb to be well established. ... 

At higher temperatures the same sample (Lounasmaa and Roach 1962, Lounasmaa and Sundstrom 1966) showed an anomalous hysteresis effect, centered around 16 K and an impurity related peak at 4.5 K. As neither of these phenomena have been satisfactorily explained, it is gratifying that Hill et al. (1974) and Wells et al. (1976) found no low temperature impurity anomaly in heat capacity measurements on S.S.E. purified terbium between 1.5 and 16 K. Thus their best results (Wells et al. 1976) indicate for Tb that y = 4.4 0.1 mJ/mole-K and 0d(O) = 178 3 K. The same arguments as above for Gd can be put forward to explain the unexpectedly low y value. The limiting 6d(0) value is in reasonable agreement with the elastic constant result of 177 K by Rosen (1968), but is considerably lower than the 187 K found from single crystal elastic constant data by Palmer (1973).t... 

The lattice contributions to the heat capacities of molten GdQ2 and TbCl2 were obtained on the assumption of their linear dependence upon the ionic radius. This estimate was made because it was accepted in this work that gadolinium and terbium dihalides have SrBr2-type structures with CN = 8. The smoothed crystal radii of Eu +, Gd +, Tb and E)y used in our calculations were taken from Chervonnyi and Chervormaya (2005c). 

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