Condensed Matter Physics, 1999, vol. 2, No. 4(20), p. 745-753, English
DOI:10.5488/CMP.2.4.745

Title: MANIFESTATIONS OF THE ELECTRON ORBITAL MOMENT IN HIGH-FREQUENCY PROPERTIES OF FERROELECTRICS WITH 3d-IONS
Author(s): I.E.Chupis (B.I.Verkin Institute For Low Temperature Physics & Engineering of National Academy of Sciences of Ukraine, 47 Lenin Ave., 310164 Kharkiv, Ukraine)

A phenomenological theory of high-frequency properties of ferroelectric and ferroelectric-ferromagnet with the 3d-ions has been elaborated based on the separate accounting for spin and orbital electron moments, electron and ion contributions to electric polarization. In the ferroelectric state, the existence of the electron orbital moment leads to the breaks in the temperature dependencies of the transverse components of dielectric susceptibility at the ferroelectric transition temperature. The values of these breaks are proportional to the square of the electron part of spontaneous polarization and the parameter of freezing of the orbital moment. Similar breaks and the decrease of the phonon frequencies in the ferroelectric state should occur in the modes which are not soft. Besides, the effect of induction of high-frequency orbital moment by electron part of electric polarization has been predicted as well. This effect would lead to the break in the temperature dependence of paramagnetic susceptibility at ferroelectric transition temperature. In the ferroelectromagnetic state, the electron orbital moment also manifests itself in $\lambda$ increase of magnetoelectric gyration ($\lambda$ is the constant of spin-orbital interaction).

Comments: Figs. 0, Refs. 8, Tabs. 0.

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