Specific Heat of Terbium Metal between 0.37 and 4.2°K

The specific heat C/sub p/ of terbium metal, measured between 0.37 and 4.2 deg K in a He/sup 3/ cryostat, could be separated by a least squares analysis irto three contributions: the lattice specific heat C/sub L/ = 0.58 T/sup 3/ (corresponding to a Debye theta = 150 deg K), the electronic specific heat C/ sub E/ = 9.05 T, and the nuclear specific heat C/sub N/ = 238 T/sup -2/ -- 11.9 T/ sup -3/ -- 4.5 T/sup -4 0.38 T/sup -5/ + 0.06 T/sup -6/ (C/sub p/ in mJ/mole deg K). C/sub N/ is due to t he splitting of the nuclear spin states by the magnetic field H/sub eff/ of the 4f electrons and by the nuclear electric quadrupole coupling. In the series expansion for C/sub N/ there are only two independent constants, the magnetic hyperfine constant a' and the quadrupole coupling constart P. Our experimental values of a' = 0.150 deg K and P = 0.021 deg K are in good agreement with results obtained by electron paramagnetic resonance and nuclear magnetic resonance techniques which gave a' = 0.152 deg K and P = 0.029 deg K. By assuming mu = 1.52 nuclear Bohr magnetons for Tb/sup 159/ one obtains H/sub eff/ = 4.1 MG. In sharp contrast with earlier results, our measurements revealed no anomalies in C/sub p/ between 1 and 4 deg K. Such anomalies thus were probably caused by impurities in the samples of the other investigators. (auth)