Magnetic anisotropy of transition-metal and rare earth compound Nd2BaNiO5

Abstract

The origin of magnetic anisotropy of each Ni2+ and Nd3+ ion in the antiferromagnetic Nd2BaNiO5, which is a related compound with the one-dimensional Haldane system Y2BaNiO5, is studied. First, we calculate the energy splitting of the orbital state of the Ni2+ ion (3F state) and that of the degenerated J state of the Nd3+ ion (4I9/2 state) due to the crystalline electric field. For the Ni2+ ion, Pryce’s spin Hamiltonian is derived and the single-ion type anisotropy constants are evaluated. The result indicates that the easy direction of the spin of the Ni2+ ion is parallel to the a axis. For the Nd3+ ion, the ground state is given by a doublet. To discuss the easy direction of the magnetic moment −gJμBJ, we calculate the magnetic susceptibility. As the result the easy direction of the magnetic moment of the Nd3+ ion is found to be parallel to the c axis. Furthermore, an effect of the magnetic dipole-dipole interaction on magnetic anisotropy is investigated.