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Summary: VOLUME 81, NUMBER 24 P H Y S I C A L R E V I E W L E T T E R S 14 DECEMBER 1998
Configurational Anisotropy in Nanomagnets
R. P. Cowburn, A. O. Adeyeye, and M. E. Welland
Nanoscale Science Group, Department of Engineering, University of Cambridge, Trumpington Street,
Cambridge CB2 1PZ, United Kingdom
(Received 4 August 1998)
A novel magneto-optical method has been used to probe the internal magnetic energy surface in
150 3 150 3 15 nm3
square Ni80Fe14Mo5 ("supermalloy") nanomagnets which were fabricated by
electron beam lithography. A strong fourfold symmetric anisotropy field of strength 365 6 20 Oe
is found, which confirms a recent prediction of the appearance of a configurational anisotropy due to
the small deviations of the magnetization from the uniform state. [S0031-9007(98)07881-8]
PACS numbers: 75.30.Gw, 75.50.Tt, 78.20.Ls
Magnetism at small length scales has in recent years
provided a wealth of scientific interest and potential
technological applications [1]. Many of these phenomena
come about by imposing a geometric restriction on the
magnet which is comparable in size to some internal
length scale of the magnet. A particularly interesting
example of confinement in magnets occurs in the zero-
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