Abstract
Micromagnetic simulations of magnetization reversal were performed for magnetic nanotubes of a finite length, L, equal to 1 and 2 μm, 50 and 100 nm radii, R, and uniaxial anisotropy with “easy axis” parallel to the tube length. I.e., we considered relatively short nanotubes with the aspect ratio L/R in the range 10–40. The non-uniform curling magnetization states on both ends of the nanotubes can be treated as vortex domain walls (DW). The domain wall length, Lc, depends on the tube geometric parameters and the anisotropy constant Ku, and determines the magnetization reversal mode, as well as the switching field value. For nanotubes with relative small values of Lc (Lc/L < 0.2) the magnetization reversal process is characterized by flipping of the magnetization in the middle uniform state. Whereas, for relative large values of Lc, in the reverse magnetic field, coupling of two vortex domain walls with opposite magnetization rotation directions results in the formation of a specific narrow Néel type DW in the middle of the nanotube. The nanotube magnetization suddenly aligns to the applied field at the switching field, collapsing the central DW.
Highlights
IntroductionOne of the central problems in the area of nanomagnetism is proper description of the magnetization reversal, the reversal modes and corresponding reversal (switching) fields [1]
One of the central problems in the area of nanomagnetism is proper description of the magnetization reversal, the reversal modes and corresponding reversal fields [1].Magnetization reversal strongly depends on the sample shape and size, as well as on the magnetic material parameters
The magnetization reversal mode description can be reduced to the motion of magnetic solitons and one domain wall approximation is sufficient for satisfactory description of the reversal
Summary
One of the central problems in the area of nanomagnetism is proper description of the magnetization reversal, the reversal modes and corresponding reversal (switching) fields [1]. The magnetization reversal and switching fields are detected via measurements of magnetic hysteresis loops. The simplest magnetic systems to study the domain wall motion are thin magnetic stripes, or wires with rectangular cross sections. The reversible part corresponds to a Néel-type domain wall nucleation between two tubular-like vortex domains with opposite circulation directions as the increasing magnetic field approaches the switching field value and the magnetization gradually decreases, forming a special magnetization configuration. The irreversible reversal takes place by collapse of the Néel-type wall in the middle of the nanotube at the switching field. We simulate the magnetization reversal by describing the intermediate magnetization states of nanotubes as the distorted vortex domain walls on both tube ends with the localization length. Since the length Lc depends on both material and geometric parameters of nanotube, the magnetization reversal reveals various modes
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