反強磁性結晶における二次の相転移

In certain types of peramagnets there are sometimes different kinds of environment of spins of the same species which are mixed and correlated with each other through the existence of spin-spin interaction. Paramagnetic resonance studies in such cases were first observed in CuSO_4・5H_2O by Bagguley and Griffith, then in K_2CuCl_4・2H_2O and Mn(HCOO)_2・2H_2O by Abe et al. Results of the susceptibility and the specific heat measurements of CuSO_4・5H_2O and CuSO_4・5H_2O by Haseda et al. convinced us the situation that two kinds of dissimilar copper ion present.
In this paper the theoretical calculation of the susceptibility and the specific heat anomaly is performed for the four sublattice model in the crystal of CuSO_4・5H_2O type.