Fabrication and structural characterization of ordered magnetic nanodot arrays over large area

IEEE Transactions on Magnetics, 2000

Acid-anodized aluminum forms amorphous alumina with long and columnar nanopores with approximately hexagonal ordering ("alumite"). Excellent hexagonal ordering of these nanopores has been achieved by 24 hours of anodization, but with restricted domain size (2-4 µm 2 ), which can be increased to 100 µm 2 with longer anodization. We have deposited Fe in disordered pores and Co in ordered pores; we can control the average length and diameter of these nanowires, but there is still a distribution of nanowire lengths. Previously, we described Fe nanowires with diameters down to 11 nm in disordered pores. Here we focus on longer (770 nm) and shorter (64 nm) Co nanowires with diameters of 25 nm in ordered pores with 100 nm pore-to-pore separation. The longer wires have an easy axis out-of-plane, with squareness 0.9, coercivity = 1900 Oe, and a fluctuation field of 5.3 Oe. The shorter wires are more isotropic, with lower coercivities ( 1300 Oe) and larger fluctuation fields 8.4 Oe. ).

Journal of Magnetism and Magnetic Materials, 2014

The magnetic properties of Ni 80 Fe 20 antidot arrays with hole diameters of 18 and 70 nm fabricated by a template-assisted method were investigated using the ferromagnetic resonance technique. Tuning the antidot arrays by changing the hole diameter enables control on the angular dependence of the ferromagnetic resonance field. The scanning electron microscope images reveal a quite regular hexagonal arrangement of the pores, however the angular dependence of the resonance field do not exhibit the sixfold symmetry expected for this symmetry. Micromagnetic simulations performed on a perfect hexagonal lattice, when compared with those made on our real system taken from the scanning microscope images, reveal that the presence of defects in the antidot lattice affects the ferromagnetic resonance field symmetry.

Applied Physics Letters, 2012

Applied Physics Letters, 2007

Journal of Physics: Conference Series, 2009

In this work, we study the magnetic structure and morphology of the Fe nanodot system fabricated by the non-lithographic method, using anodic aluminum oxide (AAO) membrane as a template. By the two-steps aluminum anodization, the AAO patterns with the hexagonal pore arrangement have been achieved. Using AAO pattern as a template, under suitable conditions we successfully deposited the iron metal in the pores by the thermal vacuum evaporation. By the exposure of the deposited system from the bottom of the AAO membrane, the hexagonal ordered Fe nanodot system has been obtained. The morphologies of the nanodot system were imaged by the Atomic Force Microscopy (AFM) and Field Emission Scanning Microscopy (FESEM) methods. The magnetic structures were investigated by the Energy Dispersive X-Ray Fluorescence Spectroscopy (EDS) and Magnetic Force Microscopy (MFM) methods. Experimental results confirmed that the MFM image of the fabricated Fe nanodot system is similar to their AFM image.

Nanoscale research letters, 2015

Arrays of epitaxial Fe3O4 nanodots were prepared using laser molecular beam epitaxy (LMBE), with the aid of ultrathin porous anodized aluminum templates. An Fe3O4 film was also prepared using LMBE. Atomic force microscopy and scanning electron microscopy images showed that the Fe3O4 nanodots existed over large areas of well-ordered hexagonal arrays with dot diameters (D) of 40, 70, and 140 nm; height of approximately 20 nm; and inter-dot distances (D int) of 67, 110, and 160 nm. The calculated nanodot density was as high as 0.18 Tb in.(-2) when D = 40 nm. X-ray diffraction patterns indicated that the as-grown Fe3O4 nanodots and the film had good textures of (004) orientation. Both the film and the nanodot arrays exhibited magnetic anisotropy; the anisotropy of the nanoarray weakened with decreasing dot size. The Verwey transition temperature of the film and nanodot arrays with D ≥ 70 nm was observed at around 120 K, similar to that of the Fe3O4 bulk; however, no clear transition was...

Applied Physics Letters

Current Applied Physics, 2007

Thin nanodotstructured metal films and heterostructured nanodot arrays (metal nanodot arrays/Si) with a high density and uniform distribution for various kinds of metals (Au, Al, Ag, Pb, Cu, Sn, and Zn) were fabricated by thermal vacuum evaporation using an anodic porous alumina membrane as a template. However, for such metals as Sn, Zn, and Pb with relatively lower melting point as compared with Al it was found that heterostructured nanodot arrays were not formed by a single stage of evaporation. For these metals, we developed a new method termed ''two step evaporation method''. The size and the arrays of dots were depended on the pore structure in the anodic porous alumina template. The technique demonstrated in this report is simple and suitable for the preparation of nanodot arrays in the large area for materials which could be vacuum evaporated.

Applied Physics Letters, 2002

Advanced Materials, 2007

Self-organized hexagonal nanodot patterns can be formed by ion bombardment on semiconductor surfaces. Here it is shown how this method can be applied to the production of ordered nanostructures of almost any type of material by transferring the pattern originally developed on an appropriate formation layer to an intercalated thin film. Our experiments using Co as the buried material have resulted in the appearance of large-area, isotropic arrays of magnetic nanoparticles. The same procedure could be used with other nonmagnetic buried layers, whether metallic, semiconducting, or heterostructure.