Understanding the domain wall dynamics is an important issue in modern magnetism. Here we present results of domain wall displacement in curved cylindrical nanowires at a constant magnetic field. We show that the average velocity of a transverse domain wall increases with curvature. Contrary to what it is observed in stripes, in a curved wire the transverse domain wall oscillates along and rotates around the nanowire with the same frequency. These results open the possibility of new oscillation-based applications.
Arrays of Co and Ni nanowires of different lengths have been prepared by electrodeposition into nanopores of alumina membranes. The dependence of the coercivity of the arrays as a function of temperature and measurement angle of the nanowires has been measured. A simple model is presented in order to explain the behavior of the magnetic properties as a function of the angle of measurement. The analytical calculations show that while for Ni nanowires demagnetization reversal in the array is driven by means of the nucleation and propagation of a transverse wall, in Co arrays the reversal mode changes from curling to coherent when the angle of measurements changes.
Nickel-rich NiFe thin films (Ni92Fe8, Ni89Fe11 and Ni83Fe17) were prepared by combining atomic layer deposition (ALD) with a subsequent thermal reduction process. In order to obtain Ni x Fe1-x O y films, one ALD supercycle was performed according to the following sequence: m NiCp2/O3, with m = 1, 2 or 3, followed by one FeCp2/O3 cycle. The supercycle was repeated n times. The thermal reduction process in hydrogen atmosphere was investigated by in situ x-ray diffraction studies as a function of temperature. The metallic nickel iron alloy thin films were investigated and characterized with respect to crystallinity, morphology, resistivity, and magnetism. As proof-of-concept magnetic properties of an array of Ni83Fe17, close to the perfect Permalloy stoichiometry, nanotubes and an isolated tube were investigated.
We have investigated numerically the angular dependence of the coercivity and remanence of cylindrical diameter modulated Ni80Fe20 nanowires. We observed that the system always starts reversing its magnetization through the thickest segment by means of a quite complex reversal process, considering the propagation of two vortex domain walls. Furthermore, we observed a transition from vortex domain walls to coherent-mode rotation for the thinnest segment as a function of the angle in which the external magnetic field is applied. In addition, we obtained a non-monotonic behavior for the coercivity and saturation field as a function of the angle at which the external magnetic field is applied. Finally, diameter modulation is an attractive way to handle over the motion of magnetic domain walls, a phenomenon proposed as a future data storage platform.
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