抄録
The specific heat of cobalt ammonium sulfate Co(NH4)2(SO4)2·6H2O in the liquid helium temperature region is investigated theoretically. The possible contributions to it are the dipole-dipole and the exchange interactions between Co2+ ions and the hyperfine interactions within each ion. Our investigation is to obtain the first two contributions. The dipole-dipole interactions are given by use of the anisotropic g-factors determined from the paramagnetic resonance. And the exchange interactions are determined by modifying the isotropic exchange interactions by the wave functions of the lowest Kramers doublet, where we took into account only the interactions with the first and second neighbouring ions. The result obtained from the moment expansion method gives CvT2⁄R=30.2×10−4 which is in good agreement with the experimental value 27×10−4. Here Cv is the interionic (dipole-dipole and exchange) part of the specific heat at moderately high temperatures, T the absolute temperature and R the gas constant.
