Magnetic Interactions in α‐MnSeO₄, α‐FeSO₄, and β‐FeSO₄

The energy distributions of neutrons scattered by α‐MnSeO₄, α‐FeSO₄, and β‐FeSO₄ in their paramagnetic state are measured by means of a time‐of‐flight technique. The values of two exchange parameters can be estimated from a simultaneous analysis of the second moment of these energy distributions and of the Néel temperature computed in the Green's function approximation. Various two‐parameter analyses are performed and checked by comparing calculated and experimental values for θ and χ(T_N). For α‐FeSO₄ the dominant interactions occur between the first and second neighbours. For β‐FeSO₄ two‐parameter analyses do not lead to a satisfactory description of all data; however, one can conclude that the interactions between third neighbours are important, in agreement with the stability conditions for the observed spin configuration.