The magnetic moments
of the three organic molecules and the cobalt surface align
very stably relative
to each other. (Photo: M. Gruber, KIT)
Organic Molecules Fixing the Magnetic Orientation of a
Cobalt Surface / Building Block for a Compact and Low-cost Storage Technology /
Publication in Nature Materials
(July 23, 2015) Organic
molecules allow producing printable electronics and solar cells with
extraordinary properties. In spintronics, too, molecules open up the unexpected
possibility of controlling the magnetism of materials and, thus, the spin of
the flowing electrons. According to what is reported in Nature Materials by a
German-French team of researchers, a thin layer of organic molecules can
stabilize the magnetic orientation of a cobalt surface. (DOI: 10.1038/NMAT4361)
“This special interaction between organic molecules and
metal surfaces could help to manufacture information storage systems in a more
simple, flexible and cheaper way,” explains Wulf Wulfhekel from KIT.
Microscopic magnets with constant orientation are used in hard disks, for
example. With a view to “printable electronics”, organic molecules indeed could
open up new simple production methods utilizing the self-organization of
molecules.
In the present study, three molecular layers of the dye
phtalocynine were applied to the surface of ferromagnetic cobalt. Whereas the
magnetic moments of the molecules alternatingly align relative to the cobalt
and relative to each other, the molecules form a so-called antiferromagnetic
arrangement. The magnetic orientation of this combination of antiferromagnetic
and ferromagnetic materials remains relatively stable even in the presence of
external magnetic fields or cooling. “Surprisingly, the “lightweight” molecule
wins this magnetic arm wrestling with the “heavyweight” ferromagnetic material
and determines the respective properties,” Wulfhekel says. Systems of
antiferromagnetic and ferromagnetic materials, among others, are used in hard
disk reading heads. So far, manufacturing of antiferromagnets has been quite
complex and time-consuming. Should molecules be suitable for use in the
production, the antiferromagnets one day will simply come out of the printer.