Low temperature heat capacities and magnetic properties of anhydrous and hydrated forms of manganous sulfate (MnSO4)

Abstract

Manganese (II) sulfate (MnSO₄), also known as manganous sulfate, has gained attention due to its low temperature magnetic properties. Following a study of its magnetic structure, manganese sulfate was proposed as being the first orthorhombic compound to have a spiral magnetic structure. It was predicted to have a three-step magnetic transition at low temperatures, which neutron diffraction studies have since confirmed. This work represents the first time that heat capacity data has been collected on MnSO₄ and MnSO₄ 0.984(H₂O) at low temperatures, which we report from 1.8 K to 300 K and comment on the presentation of the magnetic transition in the low temperature heat capacity region. Previous studies report the heat capacity of the anhydrous form above 50 K, and the data collected herein is compared with those previously published results. Theoretical fits of the heat capacity data are used to calculate the smoothed thermodynamic data, including C_p,m°, ${\Delta }_0^T$ S_m°, ${\Delta }_0^T$ H_m°, and Φ_m°.