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SM ISO690:2012 FELEA, Viorel, CONG, Phamthan, PRODAN, Lilian, TSURKAN, Vladimir, LOIDL, Alois. High-field phase transitions in the orbitally ordered multiferroic Ge V4 S8. In: Physical Review B, 2020, vol. 101, p. 0. ISSN 2469-9950. DOI: https://doi.org/10.1103/PhysRevB.101.064413 |
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Physical Review B | ||||||
Volumul 101 / 2020 / ISSN 2469-9950 /ISSNe 2469-9969 | ||||||
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DOI:https://doi.org/10.1103/PhysRevB.101.064413 | ||||||
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The high-field (H,T) phase diagram of the multiferroic lacunar spinel GeV4S8 has been studied by ultrasound, magnetization, and pyrocurrent experiments in magnetic fields up to 60 T. The title compound consists of molecular building blocks, with vanadium V4 clusters characterized by a unique electron density. These vanadium tetrahedra constitute a Jahn-Teller active entity, which drive an orbital-ordering transition at 30 K with the concomitant appearance of ferroelectricity. Ultrasound and magnetization experiments reveal sharp anomalies in magnetic fields of 46 T, which are associated with a first-order phase transition into an orbitally disordered state characterized by significant field and temperature hystereses. We report a sequence of complex magnetic, polar, and orbitally ordered states, i.e., the appearance of two orbitally ordered phases OO1 and OO2 for μ0H<45T and T<30K. Beyond the paraelectric phase we further evidenced three ferroelectric phases, FE1, FE2, and FE3. Finally, antiferromagnetic (AFM) order (T<15 K) and fully polarized ferromagnetic order (μ0H>60T) have been observed in GeV4S8. At low temperatures and for fields below 40 T, AFM order coexists with the polar phase FE3 identifying a multiferroic state. Our results demonstrate a fascinating competition of the different orders, which the material manifests in high magnetic fields and at low temperatures. |
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Cuvinte-cheie Antiferromagnetism, Ferroelectricity, Germanium, Germanium compounds, Magnetic fields, magnetization, multiferroics, phase diagrams, Sulfur compounds, Ultrasonics, vanadium |
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