Ferroelectricity in Incommensurate Magnets

Harris, A. B.

doi:10.1002/9780470022184.hmm429

Cited by 14 publications

(34 citation statements)

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“…Early examples of such a system whose ferroelectric behavior and magnetic structure have been thoroughly studied are terbium manganate, TbMnO 3 ͑TMO͒, 2,3 and nickel vanadate, Ni 3 V 2 O 8 ͑NVO͒. [4][5][6][7] A similar comprehensive analysis has recently been given for the triangular lattice compound RbFe͑MoO 4 ͒ 2 ͑RFMO͒. 8 A number of other systems have been shown to have combined magnetic and ferroelectric transitions, [9][10][11][12][13][14] but the investigation of their magnetic structure has been less systematic.…”

Section: Introductionmentioning

confidence: 98%

“…While the first part of this symmetry analysis is well known to experts, we review it here, especially because our approach is often far simpler and less technical than the standard one. However, either approach lays the groundwork for incorporating the effects of inversion symmetry, which, in the recent literature, have often been overlooked until our analysis of NVO [4][5][6][7] and TMO. 3 Inversion symmetry was also addressed by Schweizer with a subsequent correction.…”

Section: Introductionmentioning

confidence: 99%

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Landau analysis of the symmetry of the magnetic structure and magnetoelectric interaction in multiferroics

Harris

2007

Phys. Rev. B

142

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Landau analysis of the symmetry of the magnetic structure and magnetoelectric interaction in multiferroics

Harris

2007

Phys. Rev. B

142

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“…On the other hand, central to this Letter is the vector spin chirality [9], i.e., the vector product of two noncollinear spins. It is T -even and I-odd, and can produce the ferroelectric polarization in Mott insulators through the spin-orbit interaction [10,11,12,13,14,15,16,17], even for spin-1/2 systems [17,18,19].…”

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confidence: 99%

Chiral Spin Pairing in Helical Magnets

Onoda

Nagaosa

2007

Phys. Rev. Lett.

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A concept of chiral spin pairing is introduced to describe a vector-chiral liquid-crystal order in frustrated spin systems. It is found that the chiral spin pairing is induced by the coupling to phonons through the Dzyaloshinskii-Moriya interaction and the four-spin exchange interaction of the Coulomb origin under the edge-sharing network of magnetic and ligand ions. This produces two successive second-order phase transitions upon cooling: an O(2) chiral spin nematic, i.e., spin cholesteric, order appears with an either parity, and then the O(2) symmetry is broken to yield a helical magnetic order. Possible candidate materials are also discussed as new multiferroic systems.PACS numbers: 75.10. Hk, 05.50.+q, 63.70.+h, The chirality in the electronic spin texture introduced by a geometrical frustration and/or the relativistic spinorbit interaction has been one of the key concepts in strongly correlated electron systems. The scalar spin chirality [1, 2, 3], i.e., the scalar triple product of three noncoplanar spins, is odd under the time-reversal (T ) and even under the space-inversion (I), and gives rise to a large anomalous Hall effect [4,5,6,7,8]. On the other hand, central to this Letter is the vector spin chirality [9], i.e., the vector product of two noncollinear spins. It is T -even and I-odd, and can produce the ferroelectric polarization in Mott insulators through the spin-orbit interaction [10,11,12,13,14,15,16,17], even for spin-1/2 systems [17,18,19].The vector-chiral spin order is realized in conventional helical magnets. In principle, it is even possible that the chiral or parity symmetry is broken but the time-reversal symmetry is not. This state having finite spin correlation lengths is categorized into a liquid or a liquid crystal of spins, which is of our main interest, while the magnetically ordered state into a solid. The issue of the chiral spin order in the absence of any magnetic order is not only a problem of statistical mechanics, but has been intensively studied since the discovery of high-T c cuprates, and even gives a new "multiferroic" phenomenon which has attracted current great interests, as discussed below. However, conditions for the order being stabilized have not been fully understood.It has been argued that the vector or pseudoscalar chiral ordering [20,21,22] takes place separately from the XY transition in the antiferromagnetic (AF) XY model on the triangular lattice [23]. The intermediate phase is characterized by the vector-chiral order. It has also been obtained for frustrated quantum spin systems in one dimension [24], and discussed in two dimensions [25] and for odd-time states [26]. However, it usually appears only in a tiny region of the global phase diagram. For classical AF Heisenberg and XY models on stacked triangular lattices, Monte-Carlo simulations and field-theoretical analyses have suggested a single phase transition from paramagnet to helical magnet, which is either weakly first-order or a second-order one, which belongs to a different universality class from t...

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“…The hexagonal manganite RMnO 3 8,9 (where R is a rare-earth element with relatively small ionic radius) is a prototypical example of the so-called type-I multiferroics 10 with ferroelectric order at T c ∼900 K 11 and an antiferromagnetic (AFM) order at much lower temperature, T N ∼100 K 12 . A large dielectric anomaly occurs at T N 13-15 indicating strong magnetoelectric (ME) coupling in these materials.…”

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confidence: 99%

Influence of doping on the spin dynamics and magnetoelectric effect in hexagonalY0.7Lu0.3MnO3

et al. 2014

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We use inelastic neutron scattering to study spin waves and their correlation with the magnetoelectric effect in Y0.7Lu0.3MnO3. In the undoped YMnO3 and LuMnO3, the Mn trimerization distortion has been suggested to play a key role in determining the magnetic structure and the magnetoelectric effect. In Y0.7Lu0.3MnO3, we find a much smaller in-plane (hexagonal ab-plane) single ion anisotropy gap that coincides with a weaker in-plane dielectric anomaly at TN . Since both the smaller in-plane anisotropy gap and the weaker in-plane dielectric anomaly are coupled to a weaker Mn trimerization distortion in Y0.7Lu0.3MnO3 comparing to YMnO3 and LuMnO3, we conclude that the Mn trimerization is responsible for the magnetoelectric effect and multiferroic phenomenon in Y1−yLuyMnO3.PACS numbers: 75.30. Ds, 75.40.Gb, 75.50.Ee, 75.85.+t Driven by modern technology towards device miniaturization, there is considerable interest in multiferroic materials which exhibit both magnetic order and electrical polarization 1-7 . The hexagonal manganite RMnO 3 8,9 (where R is a rare-earth element with relatively small ionic radius) is a prototypical example of the so-called type-I multiferroics 10 with ferroelectric order at T c ∼900 K 11 and an antiferromagnetic (AFM) order at much lower temperature, T N ∼100 K 12 . A large dielectric anomaly occurs at T N 13-15 indicating strong magnetoelectric (ME) coupling in these materials. There has been a large amount of experimental work in recent years, with the aim to understand the microscopic mechanism for the coupling between magnetic and electric degrees of freedom in these materials. Although it is generally believed that the spin-lattice coupling plays an important role in determining the complex properties in RMnO 3 , much is unclear concerning the factors that influences the magnitude of the ME coupling 16,17 . In this Letter, we use inelastic neutron scattering (INS) and dielectric constant measurements to show that the magnitude of the ME coupling in multiferroic Y 0.7 Lu 0.3 MnO 3 is directly coupled to the strength of the Mn trimerization distortion in these materials in the AFM phase. Our results thus provide direct evidence that the Mn trimerization is responsible for the ME effect and multiferroic phenomenon in Y 1−y Lu y MnO 3 .The undoped compounds YMnO 3 and LuMnO 3 are characteristic hexagonal manganites where the Mn 3+ ions (Mn x position at x∼1/3) form a nearly ideal triangular lattice in the ab-plane above T N . YMnO 3 and LuMnO 3 undergo AFM transitions (to two different magnetic structures) at T N ∼75 K and T N ∼88 K respectively, accompanied by an isostructural transition with large atomic displacement for all atoms in the unit cell. In particular, a distinct change of the Mn atomic po- sition, namely the Mn trimerization distortion, occurs in the basal plane at T N 17 . As illustrated in Fig. 1, the Mn trimers distort in opposite directions in YMnO 3 and LuMnO 3 , expanding for YMnO 3 and contracting for LuMnO 3 . A recent theoretical study finds that the different ...

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Ferroelectricity in Incommensurate Magnets

Cited by 14 publications

References 64 publications

Landau analysis of the symmetry of the magnetic structure and magnetoelectric interaction in multiferroics

Landau analysis of the symmetry of the magnetic structure and magnetoelectric interaction in multiferroics

Chiral Spin Pairing in Helical Magnets

Influence of doping on the spin dynamics and magnetoelectric effect in hexagonalY0.7Lu0.3MnO3

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