Nanotube magnetism

Abstract

FePt and Fe3O4 nanotubes are produced by hydrogen reduction in nanochannels of porous alumina templates and investigated by electron microscopy, x-ray diffraction analysis, and magnetic measurements. Loading the templates with a Fe chloride and Pt chloride mixture followed by hydrogen reduction at 560 °C leads to the formation of ferromagnetic FePt nanotubes in the alumina pores. Using a Fe nitrate solution, thermally decomposed at 250 °C and reduced in hydrogen for 2.5 h at the same temperature, yields Fe3O4 tubes. The length of the nanotubes is about 50 μm and their diameters range from about 150 to 220 nm, depending on the thickness of the template film and the pore diameter distribution. Reflecting the different magnetocrystalline anisotropies of the compounds, the coercivities range from 0.61 kOe for Fe3O4 to 20.9 kOe for FePt. The hysteresis is explained in terms of a tubular random-anisotropy model, which yields a diameter and anisotropy dependent transition from a curling-type mode (Fe3O4) to a localized mode (FePt).

Magnetic Interaction in FeCo Alloy Nanotube Array

“…In recent years, with the development of the methods for preparing magnetic nanotubes, the synthesis of tubular nanostructures and the studies on the magnetic properties of nanotubes are pioneered in magnetic nanotechnology. The methods for fabrication include: electroless deposition [6], electrodeposition [7], wetting templates [8][9][10][11][12] and so on. Because of the potential applications demonstrated by previous studies, such as nanomedicine and biotechnology [13], ultrahigh-density magnetic storage devices [14], and nano electromechanical system device [15], magnetic nanotubes have attracted more and more attention.…”

Quantum entanglement of anisotropic magnetic nanodots

“…Such high anisotropies can be realized by exploiting the strong spin-orbit coupling of 4d, 5d, and 4f electrons, both in bulk [7,20] and in nanostructures [20,21]. Note that the typical 3d anisotropies (exploited in [22]) are much smaller: about 0.05 and 0.5 MJ/ m 3 for Fe and Co, respectively.…”

Assembly of high-anisotropy L10 FePt nanocomposite films

“…The solution-phase-based synthesis offers a convenient way to produce monodispersed FePt clusters with the size being controlled down to only a few nanometers [21], but the postannealing step is indispensable for the transformation from the disordered FCC to chemically ordered FCT structure. It is well known that template-mediated synthesis represents an elegant and effi cient approach for producing nanostructured materials [22,23]. Porous alumina templates have many advantages over others [24]; for example, they are resistant to the attack of most organic and in- organic compounds and stable at high temperature.…”