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  4. Magnetodynamical response of large-area close-packed arrays of circular dots fabricated by nanosphere lithography
 
research article

Magnetodynamical response of large-area close-packed arrays of circular dots fabricated by nanosphere lithography

Semenova, E. K.
•
Montoncello, F.
•
Tacchi, S.
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2013
Physical Review B

We report a combined experimental and theoretical study of the quasistatic hysteresis and dynamic excitations in large-area arrays of NiFe nanodisks forming a hexagonal lattice with the lattice constant of 390 nm. Arrays were fabricated by patterning a 20-nm-thick NiFe film using the etched nanosphere lithography. We have studied a close-packed (edge-to-edge separation between disks dcp = 65 nm) and an ultraclosed packed (ducp = 20 nm) array. Hysteresis loops for both arrays were qualitatively similar and nearly isotropic, i.e., independent on the in-plane external field orientation. The shape of these loops revealed that magnetization reversal is governed by the formation and expulsion of vortices inside the nanodisks. When we assumed that the nanodisks’ magnetization significantly decreases near their edges, micromagnetic simulations with material parameters deter-mined independently from continuous film measu-rements could satisfactorily reproduce the hysteresis. Despite the isotropic hysteresis, significant in-plane anisotropy of the dynamic response of the ultraclose-packed array was found experimentally by the all-electrical spin-wave spectroscopy and Brillouin light scattering. Dynamical simulations could successfully reproduce the difference between excitation spectra for fields directed along the two main symmetry axes of the hexagonal lattice. Simulations revealed that this difference is caused by the magnetodipolar interaction between nanodisks, which leads to a strong variation of the spatial distribution of the oscillation power both for bulk and edge modes as a function of the bias field orientation. Comparison of simulated and measured frequencies enabled the unambiguous identification of experimentally observed modes. Results of this systematic research are relevant both for fundamental studies of spin-wave modes in patterned magnetic structures and for the design of magnonic crystals for potential applications as, e.g., spin-wave guides and filters.

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Type
research article
DOI
10.1103/PhysRevB.87.174432
Author(s)
Semenova, E. K.
Montoncello, F.
Tacchi, S.
Dürr, G.
Sirotkin, E.
Ahmad, E.
Madami, M.
Gubbiotti, G.
Neusser, S.
Grundler, D.
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Date Issued

2013

Published in
Physical Review B
Volume

87

Issue

17

Article Number

174432

Editorial or Peer reviewed

REVIEWED

Written at

OTHER

EPFL units
LMGN  
Available on Infoscience
July 8, 2015
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/115998
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