HEAT CAPACITIES OF Fe(HCOO)2.2H2O AND Ni(HCOO)2.2H2O BETWEEN 1/4 AND 20K.

Abstract : The heat capacities of Fe(HCOO)2.2H2O and Ni(HCOO)2.2H2O have been measured between 1.4 and 20K. Peaks associated with long-range spin ordering are found at 3.74K for Fe(HCOO)2.2H2O and at 14.5K for Ni(HCOO)2.2H2O. An additional Schottky-like maximum occurs at 3K in the heat capacity of the nickel salt. These anomalies can be correlated with corresponding features of the observed magnetic susceptibilities. A unit cell of these salts contains two each of two inequivalent metal ions, types A and B. (Author)