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Open Access Nano Express

Porous silicon/Ni composites of high coercivity due to magnetic field-assisted etching

Petra Granitzer1*, Klemens Rumpf1, Toshiyuki Ohta2, Nobuyoshi Koshida2, Peter Poelt3 and Michael Reissner4

Author Affiliations

1 Institute of Physics, Karl Franzens University Graz, Universitaetsplatz 5, Graz, A-8010, Austria

2 Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo, 184-8588, Japan

3 Institute for Electron Microscopy, University of Technology Graz, Steyrergasse 17, Graz, A-8010, Austria

4 Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstr. 8, Vienna, A1040, Austria

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Nanoscale Research Letters 2012, 7:384  doi:10.1186/1556-276X-7-384

Published: 11 July 2012

Abstract

Ferromagnetic nanostructures have been electrodeposited within the pores of porous silicon templates with average pore diameters between 25 and 60 nm. In this diameter regime, the pore formation in general is accompanied by dendritic growth resulting in rough pore walls, which involves metal deposits also offering a branched structure. These side branches influence the magnetic properties of the composite system not only due to modified and peculiar stray fields but also because of a reduced interpore spacing by the approaching of adjacent side pores. To improve the morphology of the porous silicon structures, a magnetic field up to 8 T has been applied during the formation process. The magnetic field etching results in smaller pore diameters with less dendritic side pores. Deposition of a ferromagnetic metal within these templates leads to less branched nanostructures and, thus, to an enhancement of the coercivity of the system and also to a significantly increased magnetic anisotropy. So magnetic field-assisted etching is an appropriate tool to improve the structure of the template concerning the decrease of the dendritic pore growth and to advance the magnetic properties of the composite material.

Keywords:
Magnetic field-assisted anodization; Porous silicon; Magnetic nanostructures; 68.65.-k; 75.75.-c; 81.07.-b