We have used magnetic force microscopy (MFM) to investigate noncollinear helical states in multilayer nanomagnets, consisting of a stack of single domain ferromagnetic disks separated by insulating nonmagnetic spacers. The nanomagnets were fabricated from a [Co∕Si]×3 multilayer thin film structure by electron beam lithography and ion beam etching. The structural parameters (Co layer and spacer thicknesses) were optimized to obtain a clear spiral signature in the MFM contrast, taking into account the magnetostatic interaction between the layers. MFM contrast corresponding to the helical states with different helicities was observed for the optimized structure with Co layer thicknesses of 16, 11, and 8nm, and with 3nm Si spacer thickness.
We report the results of magnetic force microscopy (MFM) investigations of low-coercivity Co nanodiscs, with 50 nm lateral size and 20 nm height, fabricated by e-beam lithography and ion etching. We observed two types of MFM contrast in the form of Gaussian and ring distributions caused by strong probe-particle interaction. We compared experimentally the transformation of the MFM contrast from these low-coercivity nanodiscs caused by an external magnetic field applied in situ, and compared the experimental results with theoretical simulations.
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