Browsing by Author "Bush, A."

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    Magnetic-field-induced phase transition in BiFeO3 observed by high-field electron spin resonance: Cycloidal to homogeneous spin order
    Ruette, Benjamin; Zvyagin, Sergei; Pyatakov, Alexander P.; Bush, A.; Li, Jiefang; Belotelov, V. I.; Zvezdin, Anatoly Konstantinovich; Viehland, Dwight D. (American Physical Society, 2004-02-27)
    Bismuth ferrite is a magnetoelectric material, which simultaneously has polarization and spin orders. We have used electron spin resonance (ESR) as a local probe of the magnetic order in the magnetic-field range of 0-25 T, in the frequency domain of 115-360 GHz, and at a temperature of 4.2 K. The data reveal significant changes in the ESR spectra with increasing field, which have been analyzed by taking into account the magnetic anisotropy of the crystal and a magnetoelectric Dzyaloshinsky-Moria-like interaction. The results demonstrate an induced phase transition from an incommensurately cycloidal modulated state to one with homogeneous spin order.
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    Two-phonon coupling to the antiferromagnetic phase transition in multiferroic BiFeO(3)
    Ramirez, Mariola O.; Krishnamurthi, M.; Denev, S.; Kumar, Amit; Yang, Seung-Yeul; Chu, Ying-Hao; Saiz, Eduardo; Seidel, Jan; Pyatakov, Alexander P.; Bush, A.; Viehland, Dwight D.; Orenstein, J.; Ramesh, R.; Gopalan, Venkatraman (AIP Publishing, 2008-01-01)
    A prominent band centered at similar to 1000-1300 cm(-1) and associated with resonant enhancement of two-phonon Raman scattering is reported in multiferroic BiFeO(3) thin films and single crystals. A strong anomaly in this band occurs at the antiferromagnetic Neel temperature, T(N)similar to 375 degrees C. This band is composed of three peaks, assigned to 2A(4), 2E(8), and 2E(9) Raman modes. While all three peaks were found to be sensitive to the antiferromagnetic phase transition, the 2E(8) mode, in particular, nearly disappears at T(N) on heating, indicating a strong spin-two-phonon coupling in BiFeO(3). (c) 2008 American Institute of Physics.