BiMnO3 (BMO), ferromagnetic (FM) below Tc≃100K, was believed to also be ferroelectric (FE) due to a noncentrosymmetric C2 structure, until diffraction data indicated that its space group is the centrosymmetric C2/c. Here we present infrared phonon spectra of BMO, taken on a mosaic of single crystals, which are consistent with C2/c at any T>10K, as well as room-temperature Raman data which strongly support this conclusion. We also find that the infrared intensity of several phonons increases steadily for T→0, causing the relative permittivity of BMO to vary from 18.5 at 300 K to 45 at 10 K. At variance with FE materials of the displacive type, no appreciable softening has been found in the infrared phonons. Both their frequencies and intensities, moreover, appear insensitive to the FM transition at Tc.

Optical study of the vibrational and dielectric properties ofBiMnO3 / Mohamed, W. S.; Nucara, A.; Calestani, Gianluca; Mezzadri, Francesco; Gilioli, E.; Capitani, F.; Postorino, P.; Calvani, P.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 92:5(2015), pp. 054306-1-054306-6. [10.1103/PhysRevB.92.054306]

Optical study of the vibrational and dielectric properties ofBiMnO3

CALESTANI, Gianluca;MEZZADRI, Francesco;
2015

Abstract

BiMnO3 (BMO), ferromagnetic (FM) below Tc≃100K, was believed to also be ferroelectric (FE) due to a noncentrosymmetric C2 structure, until diffraction data indicated that its space group is the centrosymmetric C2/c. Here we present infrared phonon spectra of BMO, taken on a mosaic of single crystals, which are consistent with C2/c at any T>10K, as well as room-temperature Raman data which strongly support this conclusion. We also find that the infrared intensity of several phonons increases steadily for T→0, causing the relative permittivity of BMO to vary from 18.5 at 300 K to 45 at 10 K. At variance with FE materials of the displacive type, no appreciable softening has been found in the infrared phonons. Both their frequencies and intensities, moreover, appear insensitive to the FM transition at Tc.
Optical study of the vibrational and dielectric properties ofBiMnO3 / Mohamed, W. S.; Nucara, A.; Calestani, Gianluca; Mezzadri, Francesco; Gilioli, E.; Capitani, F.; Postorino, P.; Calvani, P.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 92:5(2015), pp. 054306-1-054306-6. [10.1103/PhysRevB.92.054306]
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2795452
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 9
  • ???jsp.display-item.citation.isi??? 9
social impact