Antiferromagnetic Structure of the Anhydrous Cobalt Sulfate CoSO₄

Abstract

The ordered spin arrangement of the orthorhombic anhydrous cobalt sulfate α–CoSO₄ (low temperature modification) in the antiferromagnetic region is considered. By assuming the four sublattice model, and by replacing the spin operators in the appropriate spin Hamiltonian by the classical spin vectors, we look for the lowest energy state of spin direction. The neutron diffraction pattern obtained by Frazer and Brown can be explained as due to the large anisotropy. The exchange integral between the nearest neighbours along c-axis J′ and that of in ab-plane J″ which give rise to the ordered spin arrangement deduced by Frazer and Brown are discussed by use of the magnetic data.