Magnetic properties of CoPt thin films and nanosized dots patterned by Laser Interference Lithography (LIL)

Abstract

Magnetic properties of Co/Pt multilayers have been extensively studied from both the practical and fundamental points of view. These multilayers have large perpendicular magnetic anisotropy, high remanent squareness and high coercivity [1]. Therefore, Co/Pt multilayer dots are possible candidates for future high-density magnetic storage media. In order to understand the magnetization process, it is essential to measure not only the properties of the array, but also of individual dots. Techniques like micro-SQUID’s can be used to measure on nano dots, however they are limited to cryogenic temperatures [2]. Alternatively, anomalous Hall effect (AHE) measurements are very sensitive and can be operated in a wide temperature range including room temperature. The AHE technique has previously been used to measure L10-FePt [3] and Co/Pt multilayer nanodots [4] and shown that the extremely high sensitivity allows detecting switching behaviour of a sub-100-nm dot. In this work we investigate the magnetic reversal of Co/Pt dots, with a focus on the switching field distribution. The arrays of dots are defined by laser interference lithography (LIL) [5]. LIL offers advantages over scanning electron-beam lithography due to its ability to define grid patterns over large, square cm, areas in a single, fast, maskless exposure