Summary: EUROPHYSICS LETTERS 15 October 1999
Europhys. Lett., 48 (2), pp. 221-227 (1999)
Designing nanostructured magnetic materials by symmetry
R. P. Cowburn, D. K. Koltsov, A. O. Adeyeye and M. E. Welland
Nanoscale Science Group, Department of Engineering, University of Cambridge
Trumpington Street, Cambridge CB2 1PZ, UK
(received 24 June 1999; accepted 30 August 1999)
PACS. 75.30Gw Magnetic anisotropy.
PACS. 75.50Tt Fine-particle systems.
PACS. 78.20Ls Magnetooptical effects.
Abstract. We have investigated experimentally the influence of the geometric shape of deep
sub-micron nanomagnets on their magnetic properties. We have used high-resolution electron
beam lithography to make arrays of nanomagnets in the size range 40-500 nm which had rectan-
gular, triangular, square and pentagonal geometries, corresponding, respectively, to rotational
symmetries of order 2, 3, 4 and 5. The parent material was Supermalloy (Ni80Fe14Mo5). We find
that an enormously wide range of magnetic properties, including some not found in conventional
unstructured materials, can be obtained by using different geometries. We demonstrate that
this is because the geometric shape imposes a strong anisotropy field of related symmetry order
on the nanomagnet via a recently discovered phenomenon called configurational anisotropy. We
show that the coercive field and remanence of these structures is determined directly by this