Magnetic Study of the Manganous Sulfates MnSO4 and MnSO4·H2O

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Abstract
The magnetization measurements up to 420 kOe made on antiferromagnetic powder specimens of MnSO4 and MnSO4·H2O between 1.6° and 70°K have revealed saturation fields of 250 and 320 kOe, respectively. The saturation value of the magnetization is in good agreement with the theoretical value for Mn2+(5 μB). The moment before saturation does not vary linearly with the applied field. This fact could be explained by spin‐wave theory or by a biquadratic term in the exchange energy. The anisotropy and the exchange fields have also been estimated from our experiments. The susceptibility versus T plot has given the Néel temperature TN and the effective moment which corresponds to the S state of Mn2+. Specific heat measurements have also been accomplished on MnSO4. They confirm our value for TN (11.5°K) and show three other peaks below the Néel temperature, two of which could correspond to the transitions theoretically forseen for this magnetic structure (cycloidal cone spiral) by Solyom.