A structural study from neutron diffraction data and magnetic properties of (R = La, rare earth)

Alonso, José Antonio; Casáis, M. T.; Martı́nez-Lope, M. J.; Martínez, José Luis; Fernández‐Díaz, M. T.

doi:10.1088/0953-8984/9/40/017

Cited by 139 publications

(153 citation statements)

References 17 publications

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“…The structural optimizations are performed for the 64-atoms cell until the forces on the relaxed cells are less than 0.005 eV/Å. The lattice parameters used in our calculations are taken from the experimental results [20].…”

Section: Computational Detailsmentioning

confidence: 99%

Modulated spin structure responsible for the magnetic-field-induced polarization switching in multiferroicTbMn2O5

Lee

Jang

2015

Phys. Rev. B

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Orthorhombic TbMn 2 O 5 (o-TMO) is a well-known multiferroic manganite with the remarkable property of polarization switching at 3 K under a bias magnetic (H) field along the a axis of P b2 1 m. To theoretically account for this outstanding observation, we have proposed a modulated spin structure under the saturated bias H field by considering the relative strength of the three relevant exchange parameters in o-TMO. The proposed modulated structure based on density-functional theory (DFT) calculations is described in terms of the spin angle φ between the neighboring Mn 4+ -Mn 3+ spin moments on the a-b plane. We have shown that the computed DFT polarization plotted as a function of φ satisfactorily accounts for the observed H -field-induced polarization switching. We have further theoretically shown that the square of the critical field strength (H c ) needed for the polarization switching is inversely proportional to the degree of the extrinsic magnetoelectric coupling. The computed partial charge density demonstrates that the H -field-induced polarization switching also accompanies with the switching in the sign of the excess valence-electron density.

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Section: Computational Detailsmentioning

confidence: 99%

Modulated spin structure responsible for the magnetic-field-induced polarization switching in multiferroicTbMn2O5

Lee

Jang

2015

Phys. Rev. B

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“…TbMn 2 O 5 crystallizes into the orthorhombic P bam spacegroup [8], with the Mn 3+ and Mn 4+ ions occupying Wyckoff 4h and 4f positions respectively [8] (Fig. 1).…”

Section: +mentioning

confidence: 99%

“…The temperature dependence of the oxygen spin polarization and the manganese ordering, confirms that the oxygen spin polarization appears at the antiferromagnetic transition, simultaneous to the onset of the ferroelectric dipole moment. We suggest that the oxygen spin polarization is a key factor the mechanism of multiferroicity in TbMn 2 O 5 .TbMn 2 O 5 crystallizes into the orthorhombic P bam spacegroup [8], with the Mn 3+ and Mn 4+ ions occupying Wyckoff 4h and 4f positions respectively [8] (Fig. 1).…”

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confidence: 93%

Antiferromagnetically Spin Polarized Oxygen Observed in MagnetoelectricTbMn2O5

et al. 2010

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We report the direct measurement of antiferromagnetic spin polarization at the oxygen sites in the multiferroic TbMn2O5, through resonant soft x-ray magnetic scattering. This supports recent theoretical models suggesting that the oxygen spin polarization is key to the magnetoelectric coupling mechanism. The spin polarization is observed through a resonantly enhanced diffraction signal at the oxygen K edge at the commensurate antiferromagnetic wavevector. Using the fdmnes code we have accurately reproduced the experimental data. We have established that the resonance arises through the spin polarization on the oxygen sites hybridized with the square based pyramid Mn 3+ions. Furthermore we have discovered that the position of the Mn 3+ ion directly influences the oxygen spin polarization.PACS numbers: 75.30. Gw, 78.70.Ck, 75.50.Ee, 75.47.Lx The ability to couple magnetism and ferroelectricity, namely the control of charges by changing the magnetic state of a material, paves the way to the development of novel multifunctional devices. Recently, the goal of being able to control the ferroelectric state by the application of a magnetic field was realized in TbMnO 3 [1], and launched a new area of research into magnetoelectric multiferroic perovskite materials. In these materials the coupling is provided through complex non-linear magnetic structures. Central to current theories[2, 3] seeking to explain the spontaneous electric polarization in perovskite manganites, is the presence of a magnetic cycloid, arising from magnetic frustration. Such a magnetic structure breaks global inversion symmetry and allows the development of a ferroelectric moment. It is interesting therefore, that in TbMn 2 O 5 , a material found to have a huge magnetoelectric coupling [4], larger even than that in TbMnO 3 , the magnetic structure was found to be almost collinear [5]. This suggests that an entirely different mechanism drives the multiferroic behavior in TbMn 2 O 5 , opening up a new route for the development of multiferroic devices. A possible mechanism has been determined by Moskvin and coworkers [6,7], who show the importance of the charge transfer between the manganese and oxygen, and the resulting spin polarization of the oxygen sites.In this letter we report the direct observation of a long range, correlated spin polarization at the oxygen sites in TbMn 2 O 5 , observed using resonant soft x-ray scattering at the oxygen K edge. This resonance is seen at the (0.5,0,0.25) antiferromagnetic wavevector corresponding to the magnetic order. Through ab-initio calculations of the incident x-ray energy dependence of the diffraction intensity we show that the ordered spin polarization arises from the oxygen sites hybridized with the Mn 3+ ions. The temperature dependence of the oxygen spin polarization and the manganese ordering, confirms that the oxygen spin polarization appears at the antiferromagnetic transition, simultaneous to the onset of the ferroelectric dipole moment. We suggest that the oxygen spin polarization is a key fact...

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“…9 Another interesting series of mixed-valence manganites with the DyMn 2 O 5 type of structure, orthorhombic RMn 2 O 5 , is in the focus of current research due to the occurrence of antiferromagnetic ordering as well as ferroelectric phase transitions at low temperatures. A significant magnetoferroelectric effect, implying a coupling between ferroelectricity and magnetic ordering, has been observed 7,[14][15][16][17][18][19][20][21][22] and is typical for these substances. 23 This suggests the possibility to control the electric polarization by an external magnetic field giving rise to parts of the above-mentioned applications.…”

Section: Introductionmentioning

confidence: 90%

EXAFS, XANES, and DFT study of the mixed-valence compoundYMn2O5: Site-selective substitution of Fe for Mn

et al. 2010

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In YMn 2 O 5 , the Mn atoms occupy two nonequivalent Wyckoff sites within the unit cell exhibiting different oxygen coordinations, i.e., the system can be characterized as a mixed-valence compound. For the formation of the orthorhombic crystal structure, Jahn-Teller distortions are assumed to play an important role. In this study, we aimed at the investigation of the crystal structure changes upon the substitution of Mn by the non-JahnTeller cation Fe 3+ . Therefore, we synthesized a series of YMn 2−x Fe x O 5 powder samples with x = 0, 0.5, and 1 by a citrate technique. We utilized extended x-ray absorption fine structure ͑EXAFS͒ and x-ray absorption near-edge structure ͑XANES͒ analysis as well as density-functional theory ͑DFT͒ to investigate the two nonequivalent Wyckoff sites within the orthorhombic crystal structure ͑confirmed for all compositions͒ occupied by transition-metal atoms. For quantitative determination of structural short-range order, all plausible options of substitution of Fe for Mn are discussed. On the basis of these evaluations, the EXAFS and XANES behavior is analyzed and appropriate crystallographic weights are assigned to the subset of structural models in accordance with the experimental data. From EXAFS analysis, using multiple-scattering theory, we conclude only the 4h Wyckoff site to be occupied by Fe ͓occupancy refined is ͑100Ϯ 3͒% in case of x =1͔. Furthermore, taking the XANES spectra into account, we are able to verify the EXAFS results and additionally explain the differences in the Mn K XANES spectra in dependence on x to be caused by changes in the dipole transitions to 4p final states. From quantitative pre-edge analysis an oxidation number of +4 for the Mn atom for x =1 is determined whereas the Fe valence is shown to be unchanged. Since the substitution process only involves one Wyckoff site, the experimentally observed limit to a maximum amount of x = 1 is explained. Additionally, a possible disorder, discussed in the literature, is not proven for our samples. With DFT calculations, the experimental findings are verified on the basis of the total energy of the different possible electronic configurations. Crystal-field effects are identified to be responsible for the site-selective substitution of Fe for Mn.

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A structural study from neutron diffraction data and magnetic properties of (R = La, rare earth)

Cited by 139 publications

References 17 publications

Modulated spin structure responsible for the magnetic-field-induced polarization switching in multiferroicTbMn2O5

Modulated spin structure responsible for the magnetic-field-induced polarization switching in multiferroicTbMn2O5

Antiferromagnetically Spin Polarized Oxygen Observed in MagnetoelectricTbMn2O5

EXAFS, XANES, and DFT study of the mixed-valence compoundYMn2O5: Site-selective substitution of Fe for Mn

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