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.

Field- and anisotropy-induced magnetic transitions and specific heat of one-dimensional XYZ ferromagnet with single-ion anisotropy

“…The Hamiltonian (4) is reduced to a diagonal form by performing a coordinate transformation from the coordinates Oxyz to the new coordinates Ox′y′z′ so that the direction of the new z'-axis coincides with the mean direction of the spins [30,35]:…”

“…The dynamical susceptibility in the Oxyz coordinate system is given by the spin thermal Green's function [30]:…”

“…Besides the exchange anisotropy in the XYZ model, the single-ion anisotropy (SIA) is also taken into account, because the SIA can be tuned in an experiment by using nuclear electric resonance [27], by mechanical control [28], or by atomic substitution [29]. In previous works [11,[30][31][32][33], the functional integral method was used to investigate the thermodynamic properties of the spin systems. With this method, the fluctuations from the mean values of the thermodynamic quantities can be found via the spin fluctuations and they can cause a drastic impact at critical points (boundaries between magnetic phases).…”

“…With this method, the fluctuations from the mean values of the thermodynamic quantities can be found via the spin fluctuations and they can cause a drastic impact at critical points (boundaries between magnetic phases). In [11] and [30], the authors used the functional integral method to study the dynamical and static properties of a monolayer spin film with the XZ model and the Ising model, respectively, but the effect of the SIA and the XYZ anisotropy have not been taken into account yet. Here, in this article, we show that the anisotropy can have an important influence on the magnetic transitions, the spin waves and the specific heat of the system for arbitrary spin.…”

Recent Progress in Nanostructured Functional Materials and Their Applications

“…From these analysis, significant increase of Currie temperature and magnetic entropy change were observed. In the second paper, enhancement of critical current density in the BiPb SrCaCuO superconductor by Na incorporation was studied by Tran et al 186) In the third paper, theoretical study on dynamical susceptibility and elementary excitations in monolayer ferroic films was conducted using Hiesenberg model by Nguyen et al 187) In the fourth category of the Advanced Spectroscopy, two cutting-edge works with advanced spectroscopic techniques were reported. In the first paper, a role of gap size and a density of the plasmonic random gold nano-sized islands for surface-enhanced Raman spectroscopy (SERS) were investigated by Nguyen et al 188) Influence of the coverage by Au nanoparticle on the SERS was studied as shown in Fig.…”