Spin Wave Excitations of a Magnetic Pillar With Dipolar Coupling Between the Layers (Preprint)

摘要

It is demonstrated analytically that the spectrum of small-amplitude spatially uniform magnetization excitations in an in-plane magnetized magnetic pillar with two ferromagnetic layers coupled by dipole-dipole interaction can be approximately described by the traditional Kittel's formula with reduced saturation magnetization and effective anisotropy field. The spectrum consists of a quasi-symmetric and a quasi-antisymmetric modes, and the apparent reduction of saturation magnetization for the quasi-symmetric mode (smaller or equal to 50 %) is much larger than for the quasi-antisymmetric mode (smaller or equal to 10 %). This effect of dynamic dipolar coupling between the nano-pillar layers could be partly responsible for the apparent reduction of static magnetization seen in many spin-torque experiments performed on magnetic nano- pillars.