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Controlling magnetic ordering in coupled nanomagnet arrays

Summary: Controlling magnetic ordering in coupled
nanomagnet arrays
R P Cowburn, A O Adeyeye and M E Welland
Nanoscale Science Group, Department of Engineering, University of
Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK
New Journal of Physics 1 (1999) 16.1­16.9 (http://www.njp.org/)
Received 3 August 1999; online 10 November 1999
Abstract. We have fabricated using high-resolution electron beam lithography
circular magnetic particles (nanomagnets) of diameter 60 nm and thickness 7 nm
out of the common magnetic alloy supermalloy. The nanomagnets were arranged
on rectangular lattices of different periods. A high-sensitivity magneto-optical
method was used to measure the magnetic properties of each lattice. We show
experimentally how the magnetic properties of a lattice of nanomagnets can
be profoundly changed by the magnetostatic interactions between nanomagnets
within the lattice. We find that simply reducing the lattice spacing in one direction
from 180 nm down to 80 nm (leaving a gap of only 20 nm between edges) causes
the lattice to change from a magnetically disordered state to an ordered state.
The change in state is accompanied by a peak in the magnetic susceptibility. We
show that this is analogous to the paramagnetic­ferromagnetic phase transition
which occurs in conventional magnetic materials, although low-dimensionality


Source: Adeyeye, Adekunle - Department of Electrical and Computer Engineering, National University of Singapore


Collections: Physics; Materials Science