Magnetic anisotropy and ferro-antiferromagnetic phase transition in LaMn 2Si 2

Abstract

The magnetic anisotropy of ternary LaMn 2Si 2 intermetallic compound has been studied in the temperature range 4–400 K. The compound have a canted ferromagnetic ordering below T C=305 K and in-plane antiferromagnetic ordering between 305 and 470 K. It has been found that the Mn sublattice exhibits a large uniaxial magnetic anisotropy with the easy magnetization direction lying along the tetragonal c -axis at T< T C. The temperature dependences of magnetic anisotropy constant K 1( T), K 2( T) were determined for T< T C. In the temperature range of the antiferromagnetic ordering above 305 K the magnetic anisotropy of the compound remains uniaxial with easy magnetization direction along the c -axis. Taking into account the magnetic structure determined by neutron diffraction experiments, a model of the magnetic interactions has been proposed, which allows to explain both the coexistence of a strong uniaxial magnetic anisotropy with a large canting angle of the magnetic structure and an uniaxial magnetic anisotropy in the antiferromagnetic phase.