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Phys. Rev. B 72, 224413 (2005) [7 pages]

Magnetostatic interaction in arrays of nanometric permalloy wires: A magneto-optic Kerr effect and a Brillouin light scattering study

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G. Gubbiotti*
Research Center SOFT-INFM-CNR, Università di Roma “La Sapienza,” I-00185, Roma, Italy

S. Tacchi
Dipartimento di Fisica, Università di Perugia, Via A. Pascoli, 06123 Perugia, Italy

G. Carlotti
INFM-CNR Research Center S3, Via Campi 213/a, 41100, Modena, Italy and Dipartimento di Fisica, Università di Perugia, Via A. Pascoli, 06123 Perugia, Italy

P. Vavassori
INFM-CNR Research Center S3, Via Campi 213/a, 41100, Modena, Italy and Dipartimento di Fisica, Università di Ferrara, Via G. Saragat 1, 44100 Ferrara, Italy

N. Singh, S. Goolaup, and A. O. Adeyeye
Information Storage Materials Laboratory, Department of Electrical and Computer Engineering, Engineering Drive 3, National University of Singapore 117576, Singapore

A. Stashkevich
LPMTM, Institut Galilée, Université Paris 13, 99 Avenue J.-B. Clément, 93430 Villetaneuse, France

M. Kostylev
St. Petersburg Electrotechnical University, 197376, St. Petersburg, Russia and School of Physics-M013, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia

Received 28 July 2005; revised 10 October 2005; published 9 December 2005

Two arrays of permalloy parallel wires, 20 nm thick, having the same width of 175 nm and different spacing of 35 and 175 nm were prepared by means of deep ultraviolet lithography and lift-off process. The effect of magnetostatic interaction on both the static and dynamic magnetic properties of arrays of wires has been investigated by means of magneto-optic and Brillouin light scattering techniques, respectively. In particular, the magnetization switching of the samples, measured by vectorial magneto-optical Kerr effect magnetometry and microscopy shows the effects of dipolar interaction in the case of 35 nm spaced wires, while in the other sample the measurements show that the wires are substantially noninteracting. The Brillouin light scattering measurements showed that for the sample with interwire spacing of 35 nm, dipolar coupling between magnetic wires leads to the formation of a collective mode which has a continuous spectrum and exists in a range of frequencies, while for the 175 nm spaced wires the spin modes are dispersionless. To quantify the investigated effects, a theory developed earlier for an isolated wire has been extended to the case of a one-dimensional array of ferromagnetic wires.

© 2005 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.72.224413
DOI:
10.1103/PhysRevB.72.224413
PACS:
75.75.+a, 76.50.+g, 78.35.+c

*Present address: Dipartimento di Fisica, Università degli Studi di Perugia, Via A. Pascoli, 06123 Perugia, Italy. Email address: gubbiotti@fisica.unipg.it