Effect of Sharp Diameter Geometrical Modulation on the Magnetization Reversal of Bi-Segmented FeNi Nanowires

Abstract

Controlling functional properties of matter and combining them for engineering a functional device is, nowadays, a common direction of the scientific community. For instance, heterogeneous magnetic nanostructures can make use of different types of geometrical and compositional modulations to achieve the control of the magnetization reversal along with the nano-entities and, thus, enable the fabrication of spintronic, magnetic data storage, and sensing devices, among others. In this work, diameter-modulated FeNi nanowires are fabricated paying special effort to obtain sharp transition regions between two segments of different diameters (from about 450 nm to 120 nm), enabling precise control over the magnetic behavior of the sample. Micromagnetic simulations performed on single bi-segmented nanowires predict a double step magnetization reversal where the wide segment magnetization switches near 16 kA/m through a vortex domain wall, while at 40 kA/m the magnetization of the narrow segment is reversed through a corkscrew-like mechanism. Finally, these results are confirmed with magneto-optic Kerr effect measurements at the transition of isolated bi-segmented nanowires. Furthermore, macroscopic vibrating sample magnetometry is used to demonstrate that the magnetic decoupling of nanowire segments is the main phenomenon occurring over the entire fabricated nanowires.

A Novel Design of a 3D Racetrack Memory Based on Functional Segments in Cylindrical Nanowire Arrays

“…• Physical: By modifying the nanowire's diameter one can easily tune its coercivity [28,29]. A segment with a larger diameter than the rest of the nanowire reverses its magnetization at lower applied magnetic fields (smaller coercivity).…”

Magnetization Reversal Process and Magnetostatic Interactions in Fe56Co44/SiO2/Fe3O4 Core/Shell Ferromagnetic Nanowires with Non-Magnetic Interlayer

“…Several methods have been successfully developed up to date to synthesize these cylindrical coaxial hetero-nanostructures. Among them, the low-cost template-assisted method can be easily combined with other techniques for the fabrication of hybrid core/shell functional nanomaterials, such as electrochemical deposition [9,10], wet-chemical route and coprecipitation [11,12], atomic layer deposition (ALD) [13][14][15][16][17], and chemical vapor deposition (CVD) [18]. For this reason, as well as for its high reproducibility and simplicity, this additive fabrication strategy constitutes one of the most widespread methods for the synthesis of one-and two-dimensional (1D and 2D) coaxial nanostructures.…”

Information storage in permalloy modulated magnetic nanowires

“…These domain walls can be moved either by applying an external magnetic field 20,24,25 , a spin-polarized current 17 , spin waves 26 or localized temperature gradients 27 . The idea is that the position of these magnetic domain walls can be precisely controlled through pinning centers, which can be generated by varying the composition of the nanowire [28][29][30] or by introducing geometrical inhomogeneities 20,24,[31][32][33][34][35][36][37][38][39] , such as modulations in its diameter during the synthesis process. Diameter modulations of the nanowire effectively allow controlling the domain wall positions since they locally reduce the magnetostatic and exchange energy in the different cross-sectional parts [40][41][42][43][44][45][46][47][48] .…”