Chapters authored
How to Characterize Cylindrical Magnetic Nanowires
Cylindrical magnetic nanowires made through the help of nanoporous alumina templates are being fabricated and characterized since the beginning of 2000. They are still actively investigated nowadays, mainly due to their various promising applications, ranging from high-density magnetic recording to high-frequency devices, passing by sensors, and biomedical applications. They also represent suitable systems in order to study the dimensionality effects on a given material. With time, the development in fabrication techniques allowed to increase the obtained nanowire complexity (controlled crystallinity, modulated composition and/or geometry, range of materials, etc.), while the improvements in nanomanipulation permitted to fabricate system based either on arrays or on single nanowires. On the other side, their increased complexity requires specific physical characterization methods, due to their particular features such as high anisotropy, small magnetic volume, dipolar interaction field between them, and interesting electronic properties. The aim of this chapter was to offer an ample overview of the magnetic, electric, and physical characterization techniques that are suitable for cylindrical magnetic nanowire investigation, of what is the specific care that one needs to take into account and which information will be extracted, with typical and varied examples.
Part of the book: Magnetic Materials
Electrical Manipulation of a Single Nanowire by Dielectrophoresis
Nanowires (NWs), due to their unique highly anisotropic characteristics, hold a great promise to be used in wide technological fields, such as building blocks for data storage and memory, advanced scanning probes, and biotechnological applications. In addition, given the high sensitivity to their environment, NWs can be used as sensor for a number of applications. The fabrication and electrical characterization of NW‐based devices can be achieved after proper placing of NWs between electrodes, which represents one of the major challenges in this field. The dielectrophoresis (DEP) method can be used to trap electrically neutral NWs by the application of an alternating electric field between a pair of electrodes. Here, we present a systematic study of DEP parameters as well as electrodes geometry for NW deposition. This method presents a suitable protocol for deposition in a useful and coherent fashion of post‐growth electrodeposited NWs and further electrical characterization. This can be used for investigation of the fundamental transport properties of individual NWs and fabrication of NW‐based devices, such as sensors and field‐effect transistors.
Part of the book: Nanowires
Stabilizing Zero-Field Skyrmions at Room-Temperature in Perpendicularly Magnetized Multilayers
Magnetic skyrmions are twirling spin structures observed in bulk, thin films, and multilayers with several features for both fundamental physics understanding and spintronic applications, i.e., nanoscale size, efficient transport under electrical current, and topological protection against defects. However, most magnetic skyrmions have been observed under the assistance of an out-of-plane magnetic field, which may limit their use in magnetic memory technologies. In this chapter, we review and present two recent mechanisms to create zero-field skyrmions at room-temperature in ferromagnetic multilayers. First, by tuning the perpendicular magnetic anisotropy (PMA) and remnant magnetization (near magnetization saturation) in unpatterned symmetric multilayer systems, it was achieved a transition from worm-like domains to isolated skyrmions. Besides, we present how to find stable zero-field skyrmions in arrays of ferrimagnetic discs by tailoring their diameter. Both methods demonstrate a robust route to stabilize zero-field skyrmions at room temperature, thus providing an important contribution to possible applications of these textures in the next generation of skyrmionics devices.
Part of the book: Magnetic Skyrmions