Static and dynamic magnetic domain configurations in electrodeposited cobalt platinum nanowires: Studied with Magnetic Force Microscope

M. Shahid Arshad^a, Kristina Žužek Rožman^a, Matej Komelj^a, Paul J. McGuiness^a, Spomenka Kobe^a,b

^aJozef Stefan Institute, Department of nano-structured materials K7, Ljubljana, Slovenia

 ^bCenter of Excellence on Nanoscience and Nanotechnology (CENN Nanocenter), Ljubljana, Slovenia

We performed magnetic domain measurements with MFM on the electrodeposited Co_65±2Pt_35±2 nanowires with the lengths of 5.5 μm and 1 μm and the diameter of 200 nm. We applied the MFM imaging and observed domain patterns on the basis of the magnetization profile in nanowires lying horizontal on mica substrate. The response of the nanowires on the variation of the external magnetic field perpendicular to the nanowire principal axis was investigated. At zero applied field the MFM image for 5.5 μm nanowire exhibits a multiple domain structure with quasiperiodic domain configuration. With an increasing field, the experimental pattern becomes more uniform in the wire, due to alignment of the magnetic moments, mostly in the direction parallel to applied magnetic field. A further increase of the external-field magnitude yields a gradual reorientation of the moments starting from the lower middle part of the nanowire towards the extremities of the wire, which ends with the majority of the moments parallel to the field direction in the saturation state. In contrast, wire with length 1 μm and diameter 200 nm showed uniform behavior. On applying magnetic field all magnetic moments abruptly reorient with external magnetic field at small field value without domain movement. This process is characterized by the change in the contrast of the MFM image. Furthermore, we have observed switching behavior due to magnetostatic interactions between two CoPt nanowires (5.5 μm) lying parallel to each other under MFM.