Magnetic Excitations in Multiferroic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>TbMnO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>: Evidence for a Hybridized Soft Mode

Senff, D.; Link, P.; Hradil, K.; Hiess, A.; Regnault, L.P.; Sidis, Y.; Aliouane, N.; Argyriou, D. N.; Braden, M.

doi:10.1103/physrevlett.98.137206

Cited by 142 publications

(161 citation statements)

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“…Experimentally this is related to a shift in the scattering wavevector to larger values for increasing the temperature above this phase transition. The lack of a large change in scattering wavevector upon excitation with 1.55 eV light suggests that under these conditions, propagation of changes in the long-range ordering of the spin system within a single domain is very slow; indeed the magnon dispersion indicates an exceedingly low group velocity for all relevant wavevectors [5,6]. Thus even if the spin system is very quickly disrupted at the sample surface, it would necessarily take a long time to propagate this perturbation into the bulk.…”

Section: Discussionmentioning

confidence: 99%

“…One of these derivatives, TbMnO3, exhibits multiferroicity below 27 K [2], and serves as a prototypical example of chiral spin order. The nature of the long range spin-cycloid ordering under equilibrium conditions has been studied and clarified using both neutron scattering [3][4][5][6] and resonant x-ray diffraction [7][8][9]. In the latter technique, soft X-rays tuned to the Mn L2 edge at 652 eV show a strong resonant enhancement giving direct information about the long-range spin order.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic order dynamics in optically excited multiferroicTbMnO3

Johnson¹,

Kubacka²,

Hoffmann³

et al. 2015

Phys. Rev. B

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We performed ultrafast time-resolved near-infrared pump, resonant soft X-ray diffraction probe measurements to investigate the coupling between the photoexcited electronic system and the spin cycloid magnetic order in multiferroic TbMnO3 at low temperatures. We observe melting of the long range antiferromagnetic order at low excitation fluences with a decay time constant of 22.3 ± 1.1 ps, which is much slower than the ~1 ps melting times previously observed in other systems. To explain the data we propose a simple model of the melting process where the pump laser pulse directly excites the electronic system, which then leads to an increase in the effective temperature of the spin system via a slower relaxation mechanism. Despite this apparent increase in the effective spin temperature, we do not observe changes in the wavevector q of the antiferromagnetic spin order that would typically correlate with an increase in temperature under equilibrium conditions. We suggest that this behavior results from the extremely low magnon group velocity that hinders a change in the spin-spiral wavevector on these time scales.2

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Magnetic order dynamics in optically excited multiferroicTbMnO3

Johnson¹,

Kubacka²,

Hoffmann³

et al. 2015

Phys. Rev. B

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“…The data shows that Mnspin ordering is first observed at T N =41K with the wave number decreasing on cooling. At T c =11K, changes discontinuously to yield a commensurate wave vector of τ = 1 4 b * [15,16,20]. Published polarization data shows that a P c state develops below T S while the polarization flops to P a at T c , coinciding with the transition to the commensurate magnetic phase [21].…”

Section: Fig 1: (Color Online) (Ab) Illustrations Of the Two Cycloidalmentioning

confidence: 99%

Flop of Electric Polarization Driven by the Flop of the Mn Spin Cycloid in MultiferroicTbMnO3

Aliouane

Schmalzl²,

Senff

et al. 2009

Phys. Rev. Lett.

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Using in-field single crystal neutron diffraction we have determined the magnetic structure of TbMnO3 in the high field P a phase. We unambiguously establish that the ferroelectric polarization arises from a cycloidal Mn spins ordering, with spins rotating in the ab plane. Our results demonstrate directly that the flop of the ferroelectric polarization in TbMnO3 with applied magnetic field is caused from the flop of the Mn cycloidal plane.PACS numbers: 61.12. Ld, 75.30.Kz, 75.47.Lx, 75.80.+q The antisymmetric Dzyaloshinski-Moriya (DM) interaction[1, 2] between two spins, S i , S i+1 separated by r i,i+1 , provides for a natural coupling between magnetism and ferroelectricity with the spontaneous ferroelectric polarization given by P s ∼ r i,i+1 × (S i × S i+1 ) [3,4,5]. This mechanism generates ferroelectricity in a wide variety of magnets such as RMnO 3 perovskites with R=Gd, Dy, and Tb, [6,7] [10,11]. In the RMnO 3 manganites the DM interaction results in cycloidal order of Mn-spins giving a spontaneous ferroelectric polarization along the c-axis (P c) ( Fig. 1(a)). The application of magnetic field results in the flop of the polarization from the c-to the a-axis and highlights a novel control of one ferroic property by an other [6]. It has been assumed that this change in the direction of the polarization reflects the flop of the Mn spin cycloid, implying that the antisymmetric DM interaction continues to be responsible for the polarization ( Fig. 1(b)) [3,12]. However, in this high field P a-phase, the commensurate magnetic wave vector for Mn is also compatible with other magneto-electric mechanisms such as exchange striction [13,14,15]. In this letter we present a determination of the magnetic structure of TbMnO 3 in a high magnetic field in the commensurate P a phase. We find that the magnetic structure of Mn-spins is characterized by an ab-cycloid that accurately describes the direction of the observed ferroelectric polarization via the DM interaction. Our finding validates the model that the polarization flops found in the perovskite manganites result from the flop of the Mn-spin cycloid.The manganite TbMnO 3 crystallizes in the orthorhombic perovskites structure Pbnm. On cooling, below T N =41K Mn spins order incommensurately point along the magnetic wave vector τ ∼ 0.275b * [5,6]. On further cooling below T S =28K, a c-axis component of the Mn moment orders with a phase shift of π/2 with respect to the b-component so as to form a cycloidal structure where Mn-spins rotate within the bc plane and around the aaxis as shown in Fig. 1(a)[5]. The axis of spin rotation defines the DM interaction, S i × S i+1 , while the distance r i,i+1 is parallel to the modulation vector τ . For this type of spin order, inversion symmetry is broken yielding for R=Tb and Dy, a ferroelectric polarization along the c-axis as indeed is observed (P s c ∼ a × b) [5,6].It is tempting to assume that the flop in the ferroelectric polarization arises from a flop in the Mn-spin spiral, but so far there is no experimental prove for ...

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“…Electromagnons were first proposed as strongly renormalized spin waves with dipolar momentum. 9 Since their discovery, electromagnons have been extensively studied in rare earth manganite compounds, namely in TbMnO 3 , where a large body of recent literature (Raman 23 , neutron 24 , and infrared 25 ) has tied the excitation to the lattice itself. The work ) 7K 15K 30K 50K 70K 85K 100K 110K 120K 130K 140K 150K 200K 250K 300K 0 100 200 300 Temperature (K) 318 has resulted in a generalized hybrid magnon-phonon mode picture of electromagnons.…”

Section: Magnetic Excitationsmentioning

confidence: 99%

Infrared phonon anomaly and magnetic excitations in single-crystal Cu3Bi(SeO3)2O
Miller
¹
,
Stephens
²
,
Martin
³

et al. 2012
Phys. Rev. B

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Infrared reflection and transmission as a function of temperature have been measured on single crystals of Cu3Bi(SeO3)2O2Cl. The complex dielectric function and optical properties along all three principal axes of the orthorhombic cell were obtained via Kramers-Kronig analysis and by fits to a Drude-Lorentz model. Below 115 K, 16 additional modes (8(E â)+6(E b )+2(E ĉ)) appear in the phonon spectra; however, powder x-ray diffraction measurements do not detect a new structure at 85 K. Potential explanations for the new phonon modes are discussed. Transmission in the far infrared as a function of temperature has revealed magnetic excitations originating below the magnetic ordering temperature (Tc ∼24 K). The origin of the excitations in the magnetically ordered state will be discussed in terms of their response to different polarizations of incident light, behavior in externally-applied magnetic fields, and the anisotropic magnetic properties of Cu3Bi(SeO3)2O2Cl as determined by d.c. susceptibility measurements.2

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Magnetic Excitations in MultiferroicTbMnO3: Evidence for a Hybridized Soft Mode

Cited by 142 publications

References 20 publications

Magnetic order dynamics in optically excited multiferroicTbMnO3

Magnetic order dynamics in optically excited multiferroicTbMnO3

Flop of Electric Polarization Driven by the Flop of the Mn Spin Cycloid in MultiferroicTbMnO3

Infrared phonon anomaly and magnetic excitations in single-crystal Cu3Bi(SeO3)2O
Miller
¹
,
Stephens
²
,
Martin
³

et al. 2012
Phys. Rev. B

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Magnetic Excitations in MultiferroicTbMnO3: Evidence for a Hybridized Soft Mode

Cited by 142 publications

References 20 publications

Magnetic order dynamics in optically excited multiferroicTbMnO3

Magnetic order dynamics in optically excited multiferroicTbMnO3

Flop of Electric Polarization Driven by the Flop of the Mn Spin Cycloid in MultiferroicTbMnO3

Infrared phonon anomaly and magnetic excitations in single-crystal Cu3Bi(SeO3)2OMiller1, Stephens2, Martin3 et al. 2012Phys. Rev. B

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Infrared phonon anomaly and magnetic excitations in single-crystal Cu3Bi(SeO3)2O
Miller
¹
,
Stephens
²
,
Martin
³

et al. 2012
Phys. Rev. B