Geometrical transformations, such as rolling a 2D ferromagnetic film into a 3D cylinder provide means to tune its magnetic properties generating different magnetic ground states 1. Rolled-up magnetic membranes with azimuthal magnetic anisotropy are very attractive due to expected much higher domain wall velocity (compare to their planar counterparts) 2 and for applications as impedance-based field sensors 1. However, a clear recipe for acquiring highly mobile azimuthal domains in a soft ferromagnetic tubular geometry is unclear. State of the art studies report the rolling of an extended ferromagnetic film (of hundreds of micro-meters), which after rolling converts into tubular geometry with 2-3 windings 1. Changes in the magnetic domain configuration in such tubular geometries may arise from modifications of the shape anisotropy in addition to stress-induced anisotropy due to rolling.
In our work, we report on rolling-induced azimuthal anisotropy in Ni₇₈Fe₂₂ stripes (as shown in figure 1a) purely due to strain, considering that curvature induced changes in shape anisotropy can be neglected due to reduced dimensions of our magnetic stripe in the azimuthal direction. For that, we employed a self-assembly rolling technology based on a polymeric platform, which allows choosing the shape and size of the magnetic structure willingly. Magnetic structures patterned on the polymeric platform can be bent controllably and hence the sign and magnitude of strain on the magnetic structure can be adjusted. We quantify the induced azimuthal magnetic anisotropy (figure 1c) by electrical measurements (figure 1b) capable of providing magnetic properties of magnetic structures hidden under the 3D polymer architecture.