Magnetic force microscopy and broadband spin wave spectroscopy on skyrmion-hosting FeGd thin films

Magnetic skyrmions are complex spin textures with non-trivial topology whose characteristics can be exploited in storage technology. In systems with perpendicular magnetic anisotropy, such as Fe/Gd multilayer films, they can be stabilized, under out-of-plane magnetic fields, by the competition between dipolar and exchange interaction. The magnetic force microscope has been used to explore the magnetic configurations of Fe/Gd amorphous multilayer samples. The MFM revealed the presence of skyrmion lattices in [Fe(0.34nm)/Gd(0.5nm)]x80 for 78-85 mT. In [Fe(0.34nm)/Gd(0.41nm)]x80, instead, stripe domains pass directly to a single domain without collapsing in skyrmion bubbles. The magnetization dynamics of [Fe(0.34nm)/Gd(0.5nm)]x80 have been investigated with all electrical spectroscopy in the GHz regime , with a focus on the resonant behaviour of skyrmions.