@article{b5be3d3ac0d34f8eadcfcf28531aab8a,
title = "Dc and high frequency magnetic properties of nanopatterned CoFe2 O4 arrays fabricated using sol-gel precursors",
abstract = "Nanostructures of ferromagnetic oxides having Curie temperatures above room temperature have potential for applications in memory devices and future spin-based electronic applications. In this article, we report on the dc and high frequency magnetic properties of arrays of elliptical CoFe2 O4 nanopillars, covering a large area, fabricated by combined electron beam lithography, and a sol-gel based chemical route. The nanopillars were successfully fabricated on insulating oxidized silicon substrates and on epitaxial thin films of ferroelectric BiFeO3. We performed magnetic force microscopy and ferromagnetic resonance spectroscopy on the arrays to probe their magnetic properties. Due to the possible existence of dominant pinning sites, the CoFe2 O4 nanopillars are not single-domain even at nanometer size scales.",
author = "Goutam Sheet and Cunliffe, {Alexandra R.} and Offerman, {Erik J.} and Folkman, {Chad M.} and Eom, {Chang Beom} and Venkat Chandrasekhar",
note = "Funding Information: This work was supported by the U.S. Department of Energy through Grant No. DE-FG02-06ER46346. We thank D. A. Dikin for help with the SEM imaging. FIG. 1. Grazing incidence x-ray diffraction spectrum on the thin film of CoFe 2 O 4 . The Miller indices corresponding to the characteristic CoFe 2 O 4 peaks are indicated. FIG. 2. (a) Magnetic moment as a function of magnetic field ( M − H ) of a CoFe 2 O 4 film on an oxidized Si substrate, with the field perpendicular to the plane of the film. (b) SEM image of the surface of the same film as in (a). Crystallites of CoFe 2 O 4 are clearly visible. (c) Topographic AFM image of the CoFe 2 O 4 film surface. (d) MFM image of the surface. FIG. 3. (a) AFM images of CoFe 2 O 4 nanopillar arrays fabricated on oxidized Si. The scan range is 15.5 μ m by 15.5 μ m . (b) Line profiles corresponding to the green and red lines in (a), showing the uniformity of the patterned structures. (c) Topographic image of a single elliptical pillar on oxidized Si, and (d) MFM image on the same pillar as in (c). FIG. 4. (a) AFM images of CoFe 2 O 4 nanopillar arrays fabricated on epitaxial BiFeO 3 . (b) Line profiles corresponding to the green and red lines in (a). (c) A surface image of the epitaxial BiFeO 3 film. (d) 3-D image of a single CoFe 2 O 4 pillar on epitaxial BiFeO 3 . The height of the pillar is 200 nm. FIG. 5. (a) Dark field optical image of the nanopillar arrays. (b) Side view of the pillars in SEM. (c) FMR spectrum with varying direction of the magnetic field with respect to the major axis of the elliptical pillars. The magnetic field is applied in the plane of the substrate where the nanopillars are grown. The two peaks in the spectra are indicated by two arrows. (d) Zoomed view of the FMR spectrum between 3000 and 4500 Oe. For (c) and (d) the curves have been offset from each other for visual clarity. The orientation of the magnetic field corresponding to each curve is shown in the index. FIG. 6. M − H curves for the CoFe 2 O 4 nanostructures generated by micromagnetic simulations using OOMMF. The solid and the dotted lines represent the M − H curves for the circular and elliptic nanoparticles respectively. ",
year = "2010",
month = may,
day = "15",
doi = "10.1063/1.3393745",
language = "English (US)",
volume = "107",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "10",
}