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SM ISO690:2012 RESCHKE, Stephan, TSIRLIN, Alexander A., KHAN, Nazir, PRODAN, Lilian, TSURKAN, Vladimir, KEZSMARKI, Istvan, DEISENHOFER, Joachim. Structure, phonons, and orbital degrees of freedom in Fe2Mo3 O8. In: Physical Review B, 2020, vol. 102, p. 0. ISSN 2469-9950. DOI: https://doi.org/10.1103/PhysRevB.102.094307 |
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Physical Review B | ||||||
Volumul 102 / 2020 / ISSN 2469-9950 /ISSNe 2469-9969 | ||||||
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DOI:https://doi.org/10.1103/PhysRevB.102.094307 | ||||||
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We report on the structural and spectroscopic characterization of the multiferroic Fe2Mo3O8. Synchrotron X-ray and neutron diffraction as well as thermal expansion measurements reveal a lattice anomaly at TN≃60K but do not show any symmetry lowering in the magnetically ordered state. The lattice parameter c exhibits a nonmonotonic behavior with a pronounced minimum around 200 K, which is also reflected in an anomalous behavior of some of the observed infrared-active optical excitations and parallels the onset of short-range magnetic order. The infrared reflectivity spectra measured between 5 and 300 K in the frequency range of 100-8000cm-1 reveal most of the expected phonon modes in comparison with the eigenfrequencies obtained by density-functional calculations. The A1 phonons show an overall hardening upon cooling, whereas a nonmonotonic behavior is observed for some of the E1 modes. These modes also show a strongly increased phonon lifetime below TN, which we associate with the quenched direction of the orbital moment in the magnetically ordered state. A similar increase is observed in the lifetime of the higher-lying d-d excitations of the tetrahedral Fe2+ site that become clearly visible below TN only. |
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Cuvinte-cheie Binary alloys, Degrees of freedom (mechanics), Iron alloys, Molybdenum alloys, Molybdenum metallography, multiferroics, Neutron diffraction, Optical lattices, phonons, Thermal expansion |
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