Coupled precession modes in indirect exchange-coupled [Pt∕Co]–Co thin films

Abstract

Magneto-optical measurements are used to investigate Pt–Co and Co layers exchange-coupled by a Pt layer. The magnetization precession was measured in a pump-probe experiment using a femtosecond laser with direct optical excitation. The competing magnetic anisotropies of the layers yield a noncollinear spin structure with a field-dependent angle between the layers. Two modes, a ferromagnetic or “acoustic” mode and an antiferromagnetic or “optic” mode, are identified from the Fourier-transformed excitation spectra, and the obtained line positions are used to estimate the interlayer exchange constants.