Transverse Dynamic Susceptibility For An Ising Spin System: An Exact Eigenvalue Equation For The Resonance Frequencies

The dynamics of an Ising system is studied assuming that a microwave radiation field is coupled to the magnetic system through the transverse spin components. The transverse dynamic susceptibility is calculated with the use of the Green-function formalism in an exact manner, without the use of any decoupling scheme. The method yields an exact eigenvalue equation for the resonance frequencies, valid for any dimension and lattice, and a physical meaning of these resonances can be given in terms of the low-lying excitations for an Ising system. Those excitations correspond to spin-flip transitions in elementary clusters which represent all the possible spin arrangements of nearest neighbors. The present method does not allow for a calculation of line intensities without the help of statistical mechanics to evaluate correlation functions. © 1984 The American Physical Society.29143343

Resonant Modes In Ising Antiferromagnets At The Critical Magnetic Field

Magnetic-resonance properties of Ising antiferromagnets near the critical field Hc are examined. It is found that Hc separates two regimes of completely different behavior. At Hc one line exhibits always vanishing amplitude. It is interesting and somewhat surprising, however, that the vanishing line is the dominant one when the field is varied from Hc in either direction. The vanishing line can be used in magnetic-resonance experiments to determine the critical field Hc. © 1987 The American Physical Society.35137167717