Search for new modulations in the BiFeO3 structure: SR diffraction and Mössbauer studies

Palewicz, Andrzej; Szumiata, T.; Przeniosło, R.; Sosnowska, I.; Margiolaki, I.

doi:10.1016/j.ssc.2006.08.046

Cited by 86 publications

(67 citation statements)

References 21 publications

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“…The refined lattice parameters and atomic positions are in good agreement with prior reports 5,6 . The temperature dependences of the lattice constants and mean square thermal displacements (squares of quantities in Table I) are shown in Fig.…”

Section: Neutron Diffractionsupporting

confidence: 88%

Anharmonic phonons and magnons in BiFeO3

Delaire

Stone

et al. 2012

Phys. Rev. B

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The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO3 were measured for temperatures 200 ≤ T ≤ 750 K , using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO3 closely resembles that of similar Fe perovskites, such as LaFeO3, despite the cycloid modulation in BiFeO3. We do not find any evidence for a spin gap. A strong T -dependence of the phonon DOS was found, with a marked broadening of the whole spectrum, providing evidence of strong anharmonicity. This anharmonicity is corroborated by large-amplitude motions of Bi and O ions observed with neutron diffraction. A clear anomaly is seen in the T dependence of Bi-dominated modes across the Néel transition. These results highlight the importance of spin-phonon coupling in this material.

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Section: Neutron Diffractionsupporting

confidence: 88%

Anharmonic phonons and magnons in BiFeO3

Delaire

Stone

et al. 2012

Phys. Rev. B

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“…At the same time, a similar hyperfine magnetic structure was observed for the perovskite-like ferrite BiFeO 3 , possessing a non-collinear magnetic structure of the cycloid type [35,36]. Thus, we can suppose that the observed inhomogeneous line broadenings of the Mössbauer spectra for AgFeO 2 reflect non-collinear spatially modulated spin ordering, which is one of the most important intrinsic features of "improper" multiferroics [4].…”

Section: Dsupporting

confidence: 55%

“…Taking into account the positive value of the correlation coefficient ¶e Q / ¶H hf » +1.6´10 -4 mm/s/kOe (see Fig.11), one may conclude that maximum hyperfine field H hf is attained for the spins of Fe 3+ ions that are directed along the V zz (H || ) axis, i. e. H || > H^, similar to the elliptical polarization (Fig 12c). Note that a similar character of hyperfine field anisotropy (H || > H^) is observed in NMR spectra for BiFeO 3 ferrite having a similar noncollinear magnetic structure of the cycloid type [35,36].…”

Section: E Origin Of Anisotropic Hyperfine Magnetic Fields In Agfeomentioning

confidence: 68%

“…In addition, we carried out a detailed analysis of the temperature dependences of hyperfine parameters, and a discussion is provided in light of the peculiarities of the electronic and magnetic states of the iron ions in 3R-AgFeO 2 . The obtained data are compared with earlier published Mössbauer data for the CuFeO 2 [27][28][29][30][31][32] and BiFeO 3 [35,36] also revealing multiferroic properties. (heating time to the desired temperatures was 10 min) in a belt-type high-pressure apparatus.…”

mentioning

confidence: 72%

“…Thus, the angular dependences of the parameters e Q (J) and H hf (J) reflect the changes in the spatially modulated magnetic structure along the length of cycloid with respect to the hexagonal unit cell. For a model fitting of the Mössbauer spectra in the Т < T N2 range, we used a procedure similar to that applied earlier for the analysis of the 57 Fe Mössbauer [33][34][35][36][37] and NMR [58] spectra of the multiferroic BiFeO 3 , which also possesses a noncollinear magnetic structure of the cycloid type. We took into account the dependences of the quadrupole shift and hyperfine magnetic field on the polar angle J between the direction of H hf (collinear, in the first approximation, with the direction of the Fe 3+ spins) and the principal axis O z of the EFG tensor, which coincides, according to our calculations, with the hexagonal axis of the AgFeO 2 lattice (Fig.…”

Section: Dmentioning

confidence: 99%

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⁵⁷Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO₂

Sobolev¹,

Rusakov²,

Moskvin³

et al. 2017

J. Phys.: Condens. Matter

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We report new results of a 57 Fe Mössbauer study of multiferroic 3R-AgFeO 2 powder samples performed in a wide temperature range, including two points, T N1 » 14 K and T N2 » 9 K, of magnetic phase transitions. At the intermediate temperature range, T N2 < T < T N1 , the 57 Fe Mössbauer spectra can be described in terms of collinear spin-density-waves (SDW) with the inclusion of many high-order harmonics, indicating that the real magnetic structure of this ferrite appears to be more complicated than a pure sinusoidally modulated SDW. The spectra at low temperatures, T < T N2 , consist of a Zeeman pattern with line broadenings and sizeable spectral asymmetry. It has been shown that the observed spectral shape is consistent with a transition to the elliptical cycloidal magnetic structure. An analysis of the experimental spectra was carried out under the assumption that the electric hyperfine interactions are modulated when the Fe 3+ magnetic moment rotates with respect to the principal axis of the EFG tensor and emergence of the strong anisotropy of the magnetic hyperfine field H hf at the 57 Fe nuclei. The large and temperatureindependent anharmonicity parameter, m » 0.78, of the cycloidal spin structure obtained from the experimental spectra results from easy-axis anisotropy in the plane of rotation of the iron spin.Analysis of different mechanisms of spin and hyperfine interactions in 3R-AgFeO 2 and its structural analogue CuFeO 2 points to a specific role played by the topology of the exchange coupling and the oxygen polarization in the delafossite structures.

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Physics and Applications of Bismuth Ferrite

2009

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BiFeO3 is perhaps the only material that is both magnetic and a strong ferroelectric at room temperature. As a result, it has had an impact on the field of multiferroics that is comparable to that of yttrium barium copper oxide (YBCO) on superconductors, with hundreds of publications devoted to it in the past few years. In this Review, we try to summarize both the basic physics and unresolved aspects of BiFeO3 (which are still being discovered with several new phase transitions reported in the past few months) and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.

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Search for new modulations in the BiFeO3 structure: SR diffraction and Mössbauer studies

Cited by 86 publications

References 21 publications

Anharmonic phonons and magnons in BiFeO3

Anharmonic phonons and magnons in BiFeO3

⁵⁷Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO₂

Physics and Applications of Bismuth Ferrite

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Search for new modulations in the BiFeO3 structure: SR diffraction and Mössbauer studies

Cited by 86 publications

References 21 publications

Anharmonic phonons and magnons in BiFeO3

Anharmonic phonons and magnons in BiFeO3

57Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO2

Physics and Applications of Bismuth Ferrite

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⁵⁷Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO₂