FIY: magneticke monopoly

[Jaroslav Lukesh]

http://www.wirelessdesignonline.com/article.mvc/Magnetic-Monopoles-Detected-In-A-Real-Magnet-0001

Magnetic Monopoles Detected In A Real Magnet For The First Time
September 4, 2009

Researchers from the Helmholtz-Zentrum Berlin für Materialien und Energie 
have, in cooperation with colleagues from Dresden, St. Andrews, La Plata and 
Oxford, for the first time observed magnetic monopoles and how they emerge 
in a real material. They published this result in the journal Science within 
the Science Express web site on Sept. 3.

Magnetic monopoles are hypothetical particles proposed by physicists that 
carry a single magnetic pole, either a magnetic North pole or South pole. In 
the material world this is quite exceptional because magnetic particles are 
usually observed as dipoles, north and south combined. However there are 
several theories that predict the existence of monopoles. Among others, in 
1931 the physicist Paul Dirac was led by his calculations to the conclusion 
that magnetic monopoles can exist at the end of tubes - called Dirac 
strings - that carry magnetic field. Until now they have remained 
undetected.

Jonathan Morris, Alan Tennant and colleagues (HZB) undertook a neutron 
scattering experiment at the Berlin research reactor. The material under 
investigation was a single crystal of Dysprosium Titanate. This material 
crystallises in a quite remarkable geometry, the so called 
pyrochlore-lattice. With the help of neutron scattering Morris and Tennant 
show that the magnetic moments inside the material had reorganised into 
so-called "Spin-Spaghetti". This name comes from the ordering of the dipoles 
themselves, such that a network of contorted tubes (Strings) develops, 
through which magnetic flux is transported. These can be made visible by 
their interaction with the neutrons which themselves carry a magnetic 
moment. Thus the neutrons scatter as a reciprocal representation of the 
Strings.

During the neutron scattering measurements a magnetic field was applied to 
the crystal by the researchers. With this field they could influence the 
symmetry and orientation of the strings. Thereby it was possible to reduce 
the density of the string networks and promote the monopole dissociation. As 
a result, at temperatures from 0.6 to 2 Kelvin, the strings are visible and 
have magnetic monopoles at their ends.

The signature of a gas made up by these monopoles has also been observed in 
heat capacity measured by Bastian Klemke (HZB). Providing further 
confirmation of the existence of monopoles and showing that they interact in 
the same way as electric charges.

In this work the researchers, for the first time, attest that monopoles 
exist as emergent states of matter, i.e. they emerge from special 
arrangements of dipoles and are completely different from the constituents 
of the material. However, alongside this fundamental knowledge, Jonathan 
Morris explains the further meaning of the results: "We are writing about 
new, fundamental properties of matter. These properties are generally valid 
for materials with the same topology, that is for magnetic moments on the 
pyrochlore lattice. For the development of new technologies this can have 
big implications. Above all it signifies the first time fractionalisation in 
three dimensions is observed."

SOURCE: Helmholtz Association of German Research Centres