Experimental study of interactions in the nanostructured Ni pillar arrays

In this work, the experimental way of measuring the interaction fields in nanoscale single domain magnet arrays is presented. This method uses a magnetic force microscopy (MFM) and an in situ electromagnet. The experiments were performed on the arrays of nanoscale nickel pillars with a period, ranging from 200 to 300 nm and a diameter of 90 nm. The up and down switching fields of the pillar were measured by applying a known field to the target pillar and raising the field until the pillar reverses the magnetization state. We used a scheme in which the MFM tip stray field and the bias field from the electromagnet are used to magnetize the individual pillars. The exact strength of the field concentrated near the tip was found experimentally by comparing the switching fields measured with and without the tip in contact with the pillars, having different switching fields. The numerical results were compared with the experimental data.