Static and Dynamic Magnetic Properties in Layered Synthetic Antiferromagnets

Synthetic antiferromagnets (SAFs), consisting of antiparallelly coupled ferromagnets, are artificial layered magnetic structures that have been widely used in magnetic storage and sensing devices. In this work, we studied the static and dynamic magnetic properties of in-plane anisotropic SAFs with a repeated Py/Ru layers. It is found that both the magnetic hysteresis loop and ferromagnetic resonance spectra depend highly on the repeating period number. In particular, a plateau is observed in the hysteresis loop at small field region for even layer SAFs, which is resulted from the almost full cancellation of net moment. While a square shaped loop is obtained in the case of odd layer SAFs in the presence of structural asymmetry. More interestingly, the initially crossed acoustic and optical resonance modes in the bilayer SAF open up a gap in the spectra of trilayer case; and more resonance branches are observed with the increase of layer number due to the differences in static positions of the individual Py magnetizations.