Magnetostatic Modes and Polaritons in Antiferromagnetic-Non-MagneticSuperlattices

摘要

The effective-medium permeability tensor is derived for an antiferromagnet-non-magnet superlattice with uniaxis parallel to the interfaces and an applied magnetic field along the uniaxis. It is used in a calculation of surface-magnetostatic-mode dispersion curves, and it is shown first that the magnetostatic modes are non-reciprocal, omega(-q) not equal to omega(q), and second that there is no magnetostatic mode for fM < 0.5 where fM is the volume fraction of the antiferromagnet. Expressions for the dispersion curves of surface polariton modes for a general direction of propagation are derived and illustrated for the Voigt geometry, propagation transverse to the magnetic field. For fM > 0.5 two real and one virtual mode are found, where a 'real' mode is one with a magnetostatic limit. For fM < 0.5 both real modes become virtual. Attenuated total reflection (ATR) curves are calculated; it is seen that they are a sensitive probe of the surface polariton spectrum.