Well-ordered La-X (X = Co, Ni and Fe) nanotubes, with the average diameter of ∼200 nm, wall thicknesses of ∼40 nm, have been fabricated into anodized aluminum oxide template by potentiostatic electrodeposition method. Various composition of La-X nanotubes were obtained by tuning the applied deposition potential. Magnetization measurements reveal that doped La could enhance the coercivity (Hc) of La-X nanotubes and their easy axis is perpendicular to the nanotube axis. There is a transition from the curling to transverse mode with increase of angle. Temperature dependent magnetization indicates the existence of superparamagnetic nanoparticles and that the surface effect results in the increase of saturation magnetization (Ms) at low temperature. Abnormal behavior of temperature dependent Hc may result from thermal excitation, magnetoelastic anisotropy, as well as oxide layer of nanotube inner surface induced coupling. These one-dimensional rare-earth transition metal nanostructures could have potential applications in novel spintronics device, ultra-small magnetic media, drug delivery, or other nanodevice.
Bibliographical noteFunding Information:
The project was supported by the State Key Project of Fundamental Research of Ministry of Science and Technology (MOST, No. 2010CB934400) and National Natural Science Foundation of China (NSFC, Grant Nos. 10934099, 11104338, and 51021061), and the partial support of Graduate Education Project of Beijing Municipal Commission of Education, the international joint projects of NSFC-The Royal Society (UK), and the partial support of K. C. Wong Education Foundation, Hong Kong.