The eigenprobtems of spin waves in a symmetrical ferromagnetic bilayered system with periodic boundary conditions are solved using the interface-rescaling approach （IRA）. The results show that interface coupling between two sublayers would not change the excitation energy of odd bulk modes, but change excitation energy of even bulk modes. We call this peculiar phenomenon the phenomenon of even bulk mode variance （PEBMV）. There are two kinds of mechanisms which cause PEBMV： phase reversal and phase translation of the magnon at the interface, corresponding, respectively, to the antiferromagnetic and ferromagnetic interface coupling cases. PEBMV embodies the selective effect of the interface on different bulk magnons.
Surface phonon-polaritons in slabs of polar ternary mixed crystals are investigated with the modified random-element-isodisplacement model and the Born-Huang approximation, based on Maxwell＇s equations with the usual boundary conditions. The numerical results of the surface phonon-polariton frequencies as functions of the wave-vector and thickness for slabs of ternary mixed crystals AlxGa1-xAs, Znx Cd1-x S,and Gax In1-x N are obtained and discussed. It is shown that there are four branches of surface phonon-polaritons in slab systems. The “two-mode” and “one-mode” behaviors of surface phonon-polaritons are also shown in their dispersion curves.
