Infrared-active phonons in the ferrimagnetic and multiferroic phases of FeCr2 S4: Evidence for structural distortions
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DEISENHOFER, Joachim, MAYR, Franz, SCHMIDT, Michael, LOIDL, Alois, TSURKAN, Vladimir. Infrared-active phonons in the ferrimagnetic and multiferroic phases of FeCr2 S4: Evidence for structural distortions. In: Physical Review B, 2019, vol. 100, p. 0. ISSN 2469-9950. DOI: https://doi.org/10.1103/PhysRevB.100.144428
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Physical Review B
Volumul 100 / 2019 / ISSN 2469-9950 /ISSNe 2469-9969

Infrared-active phonons in the ferrimagnetic and multiferroic phases of FeCr2 S4: Evidence for structural distortions

DOI: https://doi.org/10.1103/PhysRevB.100.144428

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Deisenhofer Joachim1, Mayr Franz1, Schmidt Michael1, Loidl Alois1, Tsurkan Vladimir12
 
1 University of Augsburg,
2 Institute of Applied Physics
 
Disponibil în IBN: 18 noiembrie 2019


Rezumat

We report on the temperature evolution of the infrared-active optical phonons in FeCr2S4 investigated by Fourier-transform infrared spectroscopy. The eigenfrequencies of the four triply degenerate infrared-active T1u phonons of the room-temperature cubic spinel structure shift when entering into the ferrimagnetically ordered state below TC=165K indicating strong spin-phonon coupling as reported earlier. A new mode at 200 cm-1 emerges below a temperature T∗≃115K and a splitting of the lowest-lying cubic phonon mode at about 120 cm-1 appears below the temperature TM≈60K associated with the onset of an incommensurate modulation of the magnetic structure. At the transition to the orbitally ordered and ferroelectric ground state at TOO=9K two more modes emerge at 146 and 253 cm-1 in very good agreement with the eigenfrequencies of two of the cubic Raman-active phonon modes reported by Choi et al. [J. Phys. Condens. Matter 19, 145260 (2007)JCOMEL0953-898410.1088/0953-8984/19/14/145260]. These new modes are interpreted as signatures of a symmetry lowering with a loss of inversion symmetry to induce the multiferroic orbitally ordered ground state. 

Cuvinte-cheie
Binary alloys, Fourier transform infrared spectroscopy, Ground state, phonons