Magnetic interaction parameter,

A nuclear contribution to the heat capacity arises from the two isotopes " Nd and " Nd. Heat capacity measurements by Anderson et al. (1969) (0.026-0.37 K) were used to derive values of the magnetic interaction parameters (a ) and the quadrupole coupling constants (P) for both isotopes and following the procedure as given in Section 2.4, and in Part 8.11, the variation with temperature of the nuclear contribution was derived. 

Very low-temperature calorimetiy measurements of Lounasmaa and Roach (1962) (0.37-4.2 K), Van Kempen et al. (1964) (0.05-0.89 K), Anderson et al. (1968), and Krusius et al. (1969) (0.03-0.5 K) as well as nuclear magnetic resonance (NMR) measurements by Kobayashi et al. (1967) and Sano and Itoh (1972) were used to derive the nuclear contribution to the heat capacity by determining the magnetic interaction parameter a and the quadrupole coupling constant P. Following the procedure described in Section 2.4, the selected values given in Part 13.12 were used to calculate the variation of the nuclear heat capacity with temperature. 

The isotope gives a nuclear contribution to the heat capacity. Earlier low-temperature heat capacity measurements such as those of Dreyfus et al. (1961a) (0.5-3 K), Dreyfus et al. (1961d) (0.3-1.2 K), and Parks (1962) (0.4-4.2 K) aU suffered from marked impurity levels so that only the heat capacity measurements of Krusius et al. (1974) (0.03-0.8 K) and the NMR measurements of Sano et al. (1972) could be used to determine the magnetic interaction parameter, a, and the quadrupole coupling constant, P, which following the procedure as given in Section 2.4 were then used to determine the variation of the nuclear heat capacity with temperature as summarized in Part 16.10. 

Heat capacity measurements of Holmstrom et al. (1969) (0.02-0.4 K), superseding earher measurements of Anderson et al. (1968), used the same samples as Lounasmaa and, in spite of the impurity problem, by following the procedure outlined in Section 2.4 obtained a value for the magnetic interaction parameter, a in excellent agreement with values obtained by Kalvius et al. (1963) from Mossbauer effect measurements and by Al-Kital et al. (1%7) from neutron resonance measurements. The values are summarized in Part 17.10 and those of Holmstrom et al. (1969) would lead to the following two-term expression for the nuclear heat capacity ... 

Since the magnetic interaction parameter a is of order 0.1 K, the associated Schottky anomaly in the Cp versus T curve will peak at around this temperature. Thus, for Tb, Ho and Tm we find that even in the analysis above 0.1 K we must include an estimate of the nuclear contribution (see table 5.2). 

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