Spin reorientation in manganese tutton salt Mn(NH4)2(SO4)2⋅6H2O

Abstract

It has been well know that the typical paramagnetic compound manganese Tutton salt shows an antiferromagnetism with a canted weak ferromagnetism below T N =0.175 K. Recent experiments in the temperature region of millidegree have revealed further that another transformation into the other antiferromagnetic state with hidden canting occurs at about 70 mK. A quantitative explanation of this spin reorientation phenomenon is undertaken based on the four-sublattice model. The free energies for the two possible spin structures are calculated by the molecular field approximation from the Hamiltonian which consists of the magnetic dipole interaction, the exchange interaction and the crystalline field potential. It is shown that the spin reorientation can occur for reasonable values of the exchange parameters and for either signs of D . With the use of the exchange parameters which can explain the spin reorientation, the temperature dependences of the sublattice magnetization and the magnetic susceptibilities are ...