The magnetic switching of ferromagnetic nanotubes is investigated as a function of their geometry. Two independent methods are used: Numerical simulations and analytical calculations. It is found that for long tubes the reversal of magnetization is achieved by two mechanisms: The propagation of a transverse domain wall or propagation of a vortex domain wall depending on the internal and external radii of the tube.

Ordered arrays of CoxNi1$-${}x nanowires (0<x<1) were fabricated by a template-assisted method using electrodeposition into anodic aluminum oxide membranes. Tuning of the Co-alloy composition by changing the Ni content enables control of the effective anisotropy axis, which is determined by the balance between the hcp and fcc magnetocrystalline and shape anisotropies. We report on the nanowires' structural and magnetic properties (e.g., hysteresis curves and their parameters as well as first-order reversal curve analysis), paying particular attention to their angular dependence. It is confirmed that the crystal phase of nanowires with length 2.5 $\mu${}m and diameter 35 nm shifts from hcp to fcc as the Ni content increases. That results in a significant modification of the magnetization process and, accordingly, of the magnetic properties of the array. Analytical calculations of the angular dependence of the coercivity allow us to confirm that the magnetization reversal is mostly ascribed to the propagation of a transverse domain wall. Fitting of the experiment to these calculations indicates the presence of a transverse crystalline anisotropy (ascribed to the hcp phase) in Co wires, while this changes to an axial anisotropy (fcc phase) as the Ni content increases.

The magnetization reversal in ordered arrays of iron oxide nanotubes of 50 nm outer diameter grown by atomic layer deposition is investigated theoretically as a function of the tube wall thickness $d_w$. In thin tubes $\left(d_w<13\text{nm}\right)$ the reversal of magnetization is achieved by the propagation of a vortex domain boundary, while in thick tubes $\left(d_w>13\text{nm}\right)$ the reversal is driven by the propagation of a transverse domain boundary. Magnetostatic interactions between the tubes are responsible for a decrease in the coercive field in the array. Our calculations are in agreement with recently reported experimental results. We predict that the crossover between the vortex and transverse modes of magnetization reversal is a general phenomenon on the length scale considered.

The angular dependence of the remanence and coercivity of Ni nanowire arrays produced inside the pores of anodic alumina membranes has been studied. By comparing our analytical calculations with our measurements, we conclude that the magnetization reversal in this array is driven by means of the nucleation and propagation of a transverse wall. A simple model based on an adapted Stoner–Wohlfarth model is used to explain the angular dependence of the coercivity.

Magnetic properties of arrays of nanowires produced inside the pores of anodic alumina membranes have been studied by means of vibrating sample magnetometer techniques. In these systems the length of the wires strongly influences the coercivity of the array. A simple model for the coercivity as a function of the geometry is presented which exhibits good agreement with experimental results. Magnetostatic interactions between the wires are responsible for a decrease of the coercive field.