Verification of topological magnetic properties of patterned ferromagnetic films

Abstract

Topological order of magnetic films shows promise due to its unconventional electromagnetic transport effects, but the discontinuity and the miniaturization of patterned magnetic films impose a limit on research of topological properties. In this article, a technique is proposed, the application of which improves the ease of electrical measurement in sub-micrometer-sized magnetic thin film elements. To obtain the topological Hall resistivity of the discretized magnetic textures, a ferromagnetic bilayer film was fabricated into specific geometries. Micromagnetic simulations are presented that demonstrate the topological spin distribution in an exchange coupled patterned ferromagnetic film. Experiments are performed on FePt/FeNi bilayered films that are formed with square arrays of FeNi disks on top of a continuous FePt film in a topological spin distribution. The observation of topological Hall effect was made in the FePt/FeNi film without a nanoscale Hall-bar device. The technique presented facilitates the electrical property measurement even in nanometer elements and offers a pathway for promoting spintronics applications.