Magnetostatic interaction of permalloy rectangles exhibiting a Landau state investigated by magnetotransport of single rectangles

Abstract

We study the magnetostatic interaction of submicron $\mathrm{Ni}{}_{81}$$\mathrm{Fe}{}_{19}$ rectangles arranged in a linear chain by measuring the anisotropic magnetoresistance (AMR) of a single rectangle. The rectangles have a lateral aspect ratio of 2 : 1 and are lined up with the long axis oriented side by side varying the interelement distance down to $60\phantom{\rule{0.3em}{0ex}}\mathrm{n}\mathrm{m}$. The energy density of the Landau state is determined from the hard-axis magnetization reversal for a field applied along the chain direction. As a second approach identical energy densities are deduced from the switching field (Landau to quasisingle domain state) like in the case of a Stoner-Wohlfarth particle. The results show that the impact of the magnetostatic interaction on the energy density of the Landau state in remanence is negligibly small $(<1\phantom{\rule{0.3em}{0ex}}\mathrm{k}$$\mathrm{J}$$/$$\mathrm{m}$${}^{3}$$)$. The magnetostatic interaction between field-distorted Landau states, however, is the same as for rectangles in a single domain state and is therefore governed by the compensation of surface charges at the rim. By studying rectangles with only one neighbor, the important role of symmetry on the magnetostatic interaction is shown.