Bilayered soft/hard magnetic nanowires as in-line writing heads

Abstract

Multi-segmented cylindrical nanowires (NWs) are the most promising systems for 3D racetrack memory devices, where information is stored as in-line magnetic domains. However, reading and writing information is still a challenge, as external reading/writing heads have to be implemented near the tracks. The writing component should be made of a bilayered soft/hard coupled magnetic system, so that information could be easily written by external magnetic fields. Here, we demonstrate the feasibility of using a Ni90Cu10/Fe20Co80 segmented NW as the writing element, in which magnetic information is written by applying external magnetic fields. Using low-cost template-assisted electrodeposition methods, single, bi- and multi-segmented NW hexagonal arrays of NiCu and FeCo/Au were fabricated. A throughout magnetic characterization using magnetic hysteresis loops, ferromagnetic resonance and first-order reversal curves (FORCs) revealed that the soft segment (NiCu) induced the reversal of the hard segment (FeCo) in a two-step process, reducing its coercive and effective anisotropy fields when coupled. Finally, micromagnetic simulations certified the experimental observations of a multi-step reversal process. This work demonstrates the important role of interface interactions for the future implementation of an in-line writing component in a 3D racetrack memory device, enhancing their potential applicability.