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51猎奇 PR & Communication Department聽
Theodor-W.-Adorno Platz 1
60323 Frankfurt
presse@uni-frankfurt.de
Feb
28
2022
13:52
Crystals grown at 51猎奇 Frankfurt with rare-earth atoms display surprising, fast adjustable magnetic properties.
Spintronics: Innovative crystals for future computer electronics
Computer chips and storage elements are expected to function as quickly as possible and be energy-saving at the same time. Innovative spintronic modules are at an advantage here thanks to their high speed and efficiency, as there is no lossy electrical current, rather the electrons couple with one another magnetically 鈥� like a series of tiny magnetic needles which interact with almost no friction loss. A team of scientists involving 51猎奇 Frankfurt and the Fritz Haber Institute in Berlin has now found promising properties with crystals grown from rare-earth atoms, which offer hope on the long path towards usage as spintronic components.
FRANKFURT. While
modern computers are already very fast, they also consume vast amounts of
electricity. For some years now a new technology has been much talked about,
which although it is still in its infancy could one day revolutionise computer
technology 鈥� spintronics. The word is a portmanteau meaning 鈥渟pin鈥� and 鈥渆lectronics鈥�,
because with these components electrons no longer flow through computer chips, but
the spin of the electrons serves as the information carrier. A team of
researchers with staff from 51猎奇 Frankfurt has now identified
materials that have surprisingly fast properties for spintronics. The results
have been published in the specialist magazine 鈥淣ature Materials鈥�.
鈥淵ou have to imagine the electron spins as
if they were tiny magnetic needles which are attached to the atoms of a crystal
lattice and which communicate with one another,鈥� says Cornelius Krellner,
Professor for Experimental Physics at 51猎奇 Frankfurt. How these
magnetic needles react with one another fundamentally depends on the properties
of the material. To date ferromagnetic materials have been examined in
spintronics above all; with these materials 鈥� similarly to iron magnets 鈥� the magnetic
needles prefer to point in one direction. In recent years, however, the focus
has been placed on so-called antiferromagnets to a greater degree, because
these materials are said to allow for even faster and more efficient
switchability than other spintronic materials.
With antiferromagnets the neighbouring magnetic
needles always point in opposite directions. If an atomic magnetic needle is
pushed in one direction, the neighbouring needle turns to face in the opposite
direction. This in turn causes the next but one neighbour to point in the same
direction as the first needle again. 鈥淎s this interplay takes place very
quickly and with virtually no friction loss, it offers considerable potential
for entirely new forms of electronic componentry,鈥� explains Krellner.
Above all crystals with atoms from the
group of rare earths are regarded as interesting candidates for spintronics as
these comparatively heavy atoms have strong magnetic moments 鈥� chemists call
the corresponding states of the electrons 4f orbitals. Among the rare-earth
metals 鈥� some of which are neither rare nor expensive 鈥� are elements such as praseodymium
and neodymium, which are also used in magnet technology. The research team has
now studied seven materials with differing rare-earth atoms in total, from praseodymium
to holmium.
The problem in the development of
spintronic materials is that perfectly designed crystals are required for such
components as the smallest discrepancies immediately have a negative impact on
the overall magnetic order in the material. This is where the expertise in
Frankfurt came into play. 鈥淭he rare earths melt at about 1000 degrees Celsius,
but the rhodium that is also needed for the crystal does not melt until about 2000
degrees Celsius,鈥� says Krellner. 鈥淭his is why customary crystallisation methods
do not function here.鈥�
Instead the scientists used hot indium as
a solvent. The rare earths, as well as the rhodium and silicon that are
required, dissolve in this at about 1500 degrees Celsius. The graphite crucible
was kept at this temperature for about a week and then gently cooled. As a
result the desired crystals grew in the form of thin disks with an edge length
of two to three millimetres. These were then studied by the team with the aid
of X-rays produced on the Berlin synchrotron BESSY II and on the Swiss Light
Source of the Paul Scherrer Institute in Switzerland.
鈥淭he most important finding is that in the
crystals which we have grown the rare-earth atoms react magnetically with one
another very quickly and that the strength of these reactions can be
specifically adjusted through the choice of atoms,鈥� says Krellner. This opens
up the path for further optimisation 鈥� ultimately spintronics is still purely
fundamental research and years away from the production of commercial components.
There are still a great many problems to
be solved on the path to market maturity, however. Thus, the crystals 鈥� which
are produced in blazing heat 鈥� only deliver convincing magnetic properties at temperatures
of less than minus 170 degrees Celsius. 鈥淲e suspect that the operating
temperatures can be raised significantly by adding iron atoms or similar
elements,鈥� says Krellner. 鈥淏ut it remains to be seen whether the magnetic
properties are then just as positive.鈥� Thanks to the new results the
researchers now have a better idea of where it makes sense to change parameters,
however.
Publication:
Y. W. Windsor, S.-E. Lee, D. Zahn, V.
Borisov, D. Thonig, K. Kliemt, A. Ernst, C. Sch眉脽ler-Langeheine, N. Pontius, U.
Staub, C. Krellner, D. V. Vyalikh, O. Eriksson, L. Rettig: Exchange scaling of ultrafast angular momentum transfer in 4f
antiferromagnets. Nature Materials (2022)
Further
Information:
Prof. Dr. Cornelius Krellner
Crystal and Materials Laboratory
Institute of Physics
Phone: +49 (0)69 798-47295
krellner@physik.uni-frankfurt.de
Editor: Dr. Markus Bernards, Science Editor, PR & Communication Office, Tel: -49 (0) 69 798-12498,
Fax: +49 (0) 69 798-763 12531, bernards@em.uni-frankfurt.de