Journal of Magnetism and Magnetic Materials 249 (2002) 156–162 Fabrication and magnetic properties of arrays of amorphous and polycrystalline ferromagnetic nanowires obtained by electron beam lithography J.I. Mart ! ın a , M. V! elez a , R. Morales a , J.M. Alameda a , J.V. Anguita b , F. Briones b , J.L. Vicent c, * a Depto. F! ısica, F. Ciencias, Universidad de Oviedo, 33007 Oviedo, Spain b Instituto de Microelectr ! onica de Madrid, CNM, CSIC, Isaac Newton 8, 28760 Madrid, Spain c Depto. F! ısica de Materiales, Facultad de F! ısicas, C.C. F! ısicas, Universidad Complutense, 28040 Madrid, Spain Abstract Long magnetic nanowires of amorphous and crystalline materials have been fabricated by electron beam lithography to compare their magnetic properties. The length of the wires is varied in the 200–500 mm range, and their width and the interwire distance have been reduced down to 200 nm. Magnetooptical and transport measurements show that, although the overall behavior is dominated by the shape anisotropy of the elements, wires of similar dimensions made of different materials present important differences in their magnetization reversal processes. In particular, the influence of the microstructure on the hysteresis loop characteristics has been analyzed by the comparison of Co x Si 1x alloy wires with very similar saturation magnetization, but with either amorphous or polycrystalline microstructure. r 2002 Elsevier Science B.V. All rights reserved. Keywords: Nanostructures; E-beam lithography; Magnetization reversal 1. Introduction In the last few years, there has been an increasing interest in the fabrication and study of small magnetic structures, basically driven by the need of an always higher degree of miniaturization in the fields of magnetic recording and magneto- electronics [1,2]. Even more, as typical feature sizes enter in the submicrometric range, the magnetic behavior can be drastically modified as length scales such as domain wall width, exchange length or grain size become relevant. For this reason, ordered magnetic nanostructures fabricated by nanolithography techniques [3–6] offer an inter- esting possibility as model systems in which all the geometrical dimensions can be controlled and tailored for the study of a particular problem or application [7–9]. One of the magnetic properties of nanostruc- tures most strongly affected by patterning is the effective magnetic anisotropy. Terms that are usually negligible in continuous thin films can become the most important to determine the behavior of the patterned structure. For example this is the case of shape anisotropy [10] or of magnetostatic interactions between the different *Corresponding author. Tel.: +34-91-3944559; fax: +34-91- 3944547. E-mail address: jlvicent@fis.ucm.es (J.L. Vicent). 0304-8853/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0304-8853(02)00524-3