Conţinutul numărului revistei |
Articolul precedent |
Articolul urmator |
123 0 |
SM ISO690:2012 TSURKAN, Vladimir, ZAHARKO, Oksana, SCHRETTLE, Florian, KANT, Ch., DEISENHOFER, Joachim, KRUG VON NIDDA, Hans Albrecht, FELEA, Viorel, LEMMENS, Peter, GROZA, Joanna R., QUACH, Dat V., GOZZO, Fabia, LOIDL, Alois. Structural anomalies and the orbital ground state in FeCr2S 4. In: Physical Review B - Condensed Matter and Materials Physics, 2010, vol. 81, p. 0. ISSN 1098-0121. DOI: https://doi.org/10.1103/PhysRevB.81.184426 |
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Physical Review B - Condensed Matter and Materials Physics | |
Volumul 81 / 2010 / ISSN 1098-0121 /ISSNe 1550-235X | |
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DOI:https://doi.org/10.1103/PhysRevB.81.184426 | |
Pag. 0-0 | |
Rezumat | |
We report on high-resolution x-ray synchrotron powder-diffraction, magnetic-susceptibility, sound-velocity, thermal-expansion, and heat-capacity studies of the stoichiometric spinel FeCr2S4. We provide clear experimental evidence of a structural anomaly which accompanies an orbital-order transition at low temperatures due to a static cooperative Jahn-Teller effect. At 9 K, magnetic susceptibility, ultrasound velocity, and specific heat reveal pronounced anomalies that correlate with a volume contraction as evidenced by thermal-expansion data. The analysis of the low-temperature heat capacity using a mean-field model with a temperature-dependent gap yields a gap value of about 18 K and is interpreted as the splitting of the electronic ground state of Fe2+ by a cooperative Jahn-Teller effect. This value is close to the splitting of the ground state due to spin-orbit coupling for isolated Fe2+ ions in an insulating matrix, indicating that Jahn-Teller and spin-orbit coupling are competing energy scales in this system. We argue that due to this competition, the spin-reorientation transition at around 60 K marks the onset of short-range orbital ordering accompanied by a clear broadening of Bragg reflections, an enhanced volume contraction compared to usual anharmonic behavior, and a softening of the lattice observed in the ultrasound measurements. |
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Cuvinte-cheie magnetism, Curie Temperature, Antiferromagnet |
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