title: Magnetic, structural, and electronic properties of the multiferroic compound FeTe₂O₅Br with geometrical frustration.
abstract: We report electron spin resonance (ESR), Raman scattering, and interband absorption measurements of the multiferroic FeTe₂O₅Br with two successive magnetic transitions at T(N1) = 11.0 K and T(N2) = 10.5 K. ESR measurements show all characteristics of a low-dimensional frustrated magnet: (i) the appearance of an antiferromagnetic resonance (AFMR) mode at 40 K, a much higher temperature than T(N1), and (ii) a weaker temperature dependence of the AFMR linewidth than in classical magnets, ΔH(pp)(T) ∝ T(n) with n = 2.2-2.3. Raman spectra at ambient pressure show a large variation of phonon intensities with temperature while there are no appreciable changes in phonon numbers and frequencies. This demonstrates the significant role of the polarizable Te⁴⁺ lone pairs in inducing multiferroicity. Under pressure at P = 2.12-3.04 GPa Raman spectra undergo drastic changes and absorption spectra exhibit an abrupt drop of a band gap. This evidences a pressure-induced structural transition related to changes of the electronic states at high pressures.
authors: Department of Physics, Chung-Ang University, Seoul 156-756, Republic of Korea.
authors: K-Y
authors: KY
authors: Choi
authors: I H
authors: IH
authors: Choi
authors: P
authors: P
authors: Lemmens
authors: J
authors: J
authors: van Tol
authors: H
authors: H
authors: Berger
mesh_terms: D000042:Absorption; D004583:Electrons; D058085:Iron Compounds / Q000737:chemistry*; D060328:Magnetic Phenomena; D055620:Optical Phenomena; D010087:Oxides / Q000737:chemistry*; D011312:Pressure; D013691:Tellurium / Q000737:chemistry*
chemical_list: D058085:Iron Compounds; D010087:Oxides; D013691:Tellurium