On the multiferroic skyrmion-host GaV4S8
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2018-11-14 10:45
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WIDMANN, S., RUFF, E., GUNTHER, A., KRUG VON NIDDA, Hans Albrecht, LUNKENHEIMER, Peter, TSURKAN, Vladimir, BORDACS, Sandor, KEZSMARKI, Istvan, LOIDL, Alois. On the multiferroic skyrmion-host GaV4S8. In: Philosophical Magazine, 2017, nr. 36(97), pp. 3428-3445. ISSN 1478-6535. DOI: https://doi.org/10.1080/14786435.2016.1253885
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Philosophical Magazine
Numărul 36(97) / 2017 / ISSN 1478-6535

On the multiferroic skyrmion-host GaV4S8

DOI: https://doi.org/10.1080/14786435.2016.1253885

Pag. 3428-3445

Widmann S.1, Ruff E.1, Gunther A.1, Krug Von Nidda Hans Albrecht1, Lunkenheimer Peter1, Tsurkan Vladimir12, Bordacs Sandor3, Kezsmarki Istvan341, Loidl Alois1
 
1 University of Augsburg,
2 Institute of Applied Physics, Academy of Sciences of Moldova,
3 MTA-BME Lendület Magneto-optical Spectroscopy Research Group, Budapest,
4 Budapest University of Technology and Economics, Department of Physics, Budapest
 
Disponibil în IBN: 8 decembrie 2017


Rezumat

The lacunar spinel GaV4S8 exhibits orbital ordering at 44 K and shows a complex magnetic phase diagram below 12.7 K, which includes ferromagnetic and cycloidal spin order. At low but finite external magnetic fields, Néel-type skyrmions are formed in this material. Skyrmions are whirl-like spin vortices that have received great theoretical interest because of their non-trivial spin topology and that are also considered as basic entities for new data-storage technologies. Interestingly, we found that the orbitally ordered phase shows sizable ferroelectric polarisation and that excess spin-driven polarisations appear in all magnetic phases, including the skyrmion-lattice phase. Hence, GaV4S8 shows simultaneous magnetic and polar order and belongs to the class of multiferroics materials that attracted enormous attention in recent years. Here, we summarise the existing experimental information on the magnetic, electronic and dielectric properties of GaV4S8. By performing detailed magnetic susceptibility, resistivity, specific heat and dielectric experiments, we complement the low-temperature phase diagram. Specifically, we show that the low-temperature and low-field ground state of GaV4S8 seems to have a more complex spin configuration than purely collinear ferromagnetic spin order. In addition, at the structural Jahn–Teller transition the magnetic exchange interaction changes from antiferromagnetic to ferromagnetic. We also provide experimental evidence that the vanadium V4 clusters in GaV4S8 can be regarded as molecular units with spin 1/2. However, at high temperatures deviations in the susceptibility show up, indicating that either the magnetic moments of the vanadium atoms fluctuate independently or excited states of the V4 molecule become relevant.

Cuvinte-cheie
Lacunar spinels, multiferroicity, orbital order, skyrmions,

phase diagrams