Abstract
Realising the promise of next-generation magnetic nanotechnologies is contingent on the development of novel methods for controlling magnetic states at the nanoscale. There is currently demand for simple and flexible techniques to access exotic magnetisation states without convoluted fabrication and application processes. 360° domain walls (metastable twists in magnetisation separating two domains with parallel magnetisation) are one such state, which is currently of great interest in data storage and magnonics. Here, we demonstrate a straightforward and powerful process whereby a moving magnetic charge, provided experimentally by a magnetic force microscope tip, can write and manipulate magnetic charge states in ferromagnetic nanowires. The method is applicable to a wide range of nanowire architectures with considerable benefits over existing techniques. We confirm the method’s efficacy via the injection and spatial manipulation of 360° domain walls in Py and Co nanowires. Experimental results are supported by micromagnetic simulations of the tip-nanowire interaction.
Highlights
Magnetic nanostructures can be characterised by maps of their magnetic charge distribution
To confirm the viability of the method we demonstrate the injection and subsequent manipulation of a bound magnetic charge pair composed of two transverse domain walls (DWs), known as a 360◦ DW 15. 360◦ DWs are currently of great interest in data storage and magnonics, as well as intriguing topological defects in their own right
The constituent 180◦ DWs can clearly be seen to possess twice the magnitude of the end charges and no other magnetic charges are present in the wire
Summary
Magnetic nanostructures can be characterised by maps of their magnetic charge distribution. Existing methods for the injection of magnetic charge into nanostructures rely on complex solenoid-based write heads 4, subjecting whole devices containing injection pads to global field sequences [5,6,7,8,9,10] or using complex nanowire geometries to locally apply pulsed Oersted fields [11,12,13,14]. 360◦ DWs are currently of great interest in data storage and magnonics, as well as intriguing topological defects in their own right They have been proposed as candidates for high-density data storage 16 including magnetoresistive random access memory (MRAM) systems [11,17,18] and as phase-shifting and frequency doubling magnonic circuit elements as well as spin-wave generators 20. The technique described in this work requires no global field and as such offers considerable benefits
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