Exchange Interaction via Crystal-Field Excited States and Its Importance in CsCoCl₃

Abstract

The low-energy effective Hamiltonian is derived for a typical quasi-one-dimensional Ising-like antiferromagnet CsCoCl 3 . In contrast to previous treatments, in which only the processes within the crystal-field ground Kramers doublet are considered, second-order processes via crystal-field excited states are also taken into account in the present paper. They result in a new term, which is essentially a next-nearest neighbor ferromagnetic exchange whose anisotropy is different from the nearest-neighbor exchange. By including the new term the magnetization curve and ESR in CsCoCl 3 are analyzed to show that those experiments can be explained in a way consistent with other experiments. Related theories on CsCoCl 3 are discussed in this connection.