SPIN-CLUSTER RESONANCE IN ISING SPIN SYSTEM

Detailed analysis of a new type magnetic resonance in an Ising spin antiferromagnet is reported. It was found that in a strongly anisotropic ferro- or antiferromagnetic crystal such as CoCl22H2O, non-uniform magnetic resonances with the selection rule Δm=±1, where m is the number of spins in the short range order spin cluster directed oppositely to the majority spins, can be excited. Examples of such a non-uniform spin wave excitation, thermal excitation of the cluster and the spin-cluster resonance in CoCl22H2O, are discussed using a model of the one-dimentional Ising spin system. The experimental result seems to be explained more satisfactorily when a weak third neighbor interchain exchange interaction J3 is taken into account. An extensive consideration of the spin-cluster resonance in more general Ising spin system is presented. © 1968, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.