Dynamical Susceptibility and Elementary Excitations in Monolayer Ferroic Films Described by XZ Heisenberg Model

Abstract

The dynamical susceptibility and finite temperature collective excitations in monolayer spin film are calculated using the anisotropic exchange XZ-Heisenberg model for different spin magnitude and the functional integral method. Combining mean field and Gaussian approximation, it is shown that the internal transverse field induced by internal transverse exchange interaction, leads to a decrease (increase) of the spin wave energy in the temperature region below (above) the spin reorientation temperature. This temperature is of the same nature as the critical temperature of the transverse Ising model studied previously. Reduction of the external spin reorientation transverse field (the critical tuning parameter) by intrinsic transverse exchange is demonstrated.