Oscillating exchange and spin wave stiffness in magnetic monolayers

Spin waves in a ferromagnetic monolayer are investigated taking into accoun t indirect exchange [Ruderman-Kittel-Kasuya-Yosida (RKKY)] interaction medi ated by electrons of a nonmagnetic metal substrate. Strong anomalies are fo und in the spin wave stiffness when spin lattice-line distances are close t o the RKKY wavelength. Conditions for such coincidence and its relevance in epitaxial magnetic layers on fee metals are discussed taking into account realistic Fermi surface shapes, which further enhance the magnitude of the predicted effect but may change its sign. [S0163-1829(99)03402-5].