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Magnetic Monopoles in a Metallic Compound

“Kagome Spin Ice” Behaviour Experimentally Demonstrated

Jülich/Garching, 23 March 2020 – If you break a bar magnet in two, each of the two pieces will subsequently possess a north and south pole. So far, independent mobile magnetic monopoles have only been found in a single class of magnetic crystals. An international team of researchers, including scientists from Forschungszentrum Jülich, has now discovered monopoles in a “Kagome spin ice” material, which is electrically conductive and could therefore offer great potential in scientific and practical applications.

The scientists carried out essential parts of the experimental investigations on the intermetallic compound HoAgGe with a research instrument jointly operated by Forschungszentrum Jülich and RWTH Aachen University at the Heinz Maier-Leibnitz Zentrum in Garching near Munich. Using the high-field superconducting magnet recently commissioned at the neutron diffractometer POLI, they could determine the orientation of the single interacting magnetic moments of the atoms in the crystal lattice, the so-called magnetic structure. “This can only be done by neutron diffraction,” explains the instrument scientist, Dr. Vladimir Hutanu. “With POLI, we can perform these measurements precisely as a function of temperature and magnetic field. We use the instrument to study complex magnetic structures also in other materials with application potential, such as novel quantum materials, for example, representing a research focus at the Jülich Centre for Neutron Science (JCNS).” The scientists from Jülich and Aachen carried out both the neutron measurements and also participated in the analysis of the results, in cooperation with their international colleagues.

In HoAgGe besetzten Holmium-Spins die Ecken von Dreiecken, die zu einem Kagome-Muster geordnet sind.In HoAgGe, the Ho spins occupy a Kagome structure. The arrows indicate the orientation of spins (left), following the ice rule in triangles: “two-in-one-out”, namely one positive magnetic charge, or “one-in-two-out”, namely one negative magnetic charge. Thus, the ground state can also be viewed as a honeycomb of magnetic monopole quasiparticles (right).
Copyright: Universität Augsburg

Originalpublikation: Kan Zhao, Hao Deng, Hua Chen, Kate A. Ross, Vaclav Petříček, Gerrit Guenther, Margarita Russina, Vladimir Hutanu und Philipp Gegenwart: Realization of the kagome spin ice state in a frustrated intermetallic compound. Science, 3 Mar 2020: Vol. 367, Issue 6483, pp. 1218-1223, DOI: 10.1126/science.aaw1666

Further information:

Detailed information in the press release from Augsburg University, “Magnetic measurements reveal „Kagome-Spin-Ice” state” from March 18, 2020

Website of Jülich Centre for Neutron Science – Quantum Materials and Collective Phenomena (JCNS-2):

Website of the Heinz Maier-Leibnitz Zentrum

Website of the Institute of Crystallography, RWTH Aachen University

Contact:

Dr. Vladimir Hutanu, Dr. Hao Deng
Forschungszentrum Jülich/RWTH Aachen
JSNC Outstation at Heinz Maier-Leibnitz Zentrum
Tel: +49 89 289-12153
E-Mail: v.hutanu@fz-juelich.de, hao.deng@frm2.tum.de

Press contact:

Angela Wenzik, Science Journalist
Forschungszentrum Jülich
Tel: +49 2461 61-6048
E-Mail: a.wenzik@fz-juelich.de