抄録
A curious antiferromagnetic resonance in CoCl26H2O was investigated in detail at the microwave region. This resonance was first observed by one of the present authors several years ago and reported without any reasonable explanation. In the present study, it becomes clear that the resonance can be observed only near the critical hyperbola with a half frequency of the critical field resonance. Considering the various experimental results including both the antiferromagnetic resonance and magnetostriction measurements, we concluded that the newly obtained resonance mode corresponds to the second harmonic oscillation of the critical field resonance connected with the magnetostrictive and anisotropic exchange couplings. It is shown that a sudden change in lattice constants observed near the critical field makes it possible to produce the second order higher harmonic oscillation of the spin system in antiferromagnetic CoCl26H2O.
