First-Principles Modeling of Multiferroic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>R</mml:mi><mml:msub><mml:mi>Mn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="bold">O</mml:mi><mml:mn>5</mml:mn></mml:msub></mml:math>

Cao, Kun; Guo, Guang‐Can; Vanderbilt, David; He, Lixin

doi:10.1103/physrevlett.103.257201

Cited by 63 publications

(75 citation statements)

References 27 publications

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“…We calculate the ordering temperature by forcing all exchange interactions to be ferromagnetic, and get T c = 311 K by a Monte Carlo simulation. This temperature is only about 1.5 times greater than the T c of the AFM1 phase from simulations (In RMn 2 O 5 [27], the ratio is approximately 3 -4. ), which also indicate that the spin frustration is weak in CuO.…”

Section: −5åmentioning

confidence: 69%

Origin of Ferroelectricity in High-TcMagnetic Ferroelectric CuO

et al. 2012

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"Magnetic ferroelectric" has been found in a wide range of spiral magnets. However, these materials all suffer from low critical temperatures, which are usually below 40 K, due to strong spin frustration. Recently, CuO has been found to be multiferroic at much higher ordering temperature (∼ 230K). To clarify the origin of the high ordering temperature in CuO, we investigate the structural, electronic and magnetic properties of CuO via first-principles methods. We find that CuO has very special nearly commensurate spiral magnetic structure, which is stabilized via the Dzyaloshinskii-Moriya interaction. The spin frustration in CuO is relatively weak, which is one of the main reasons that the compound have high ordering temperature. We propose that high Tc magnetic ferroelectric materials can be found in double sublattices of magnetic structures similar to that of CuO. PACS numbers: 75.85.+t, Magnetic ferroelectric materials in which ferroelectricity is induced by magnetic ordering, have attracted intensive interests [1,2]. The strong magnetoelectric (ME) coupling in these materials opens up a new path to the design of multifunctional devices that allow the control of charges by the application of magnetic fields or spins by applying voltages. So far, almost all magnetic ferroelectric materials are strongly frustrated magnets [2]. Frustrated magnets have very low ordering temperatures (∼ 30 -40 K), several times smaller than the temperatures expected from their spin interaction strengths. Low critical temperature is one of the major factors that limit the applications of these important materials. Therefore a new mechanism that allows high temperature magnetic ferroelectric materials is critical.Recently, CuO was found to be multiferroic at T c =230 K, which is much higher than the critical temperatures of all other magnetic ferroelectric materials [3]. However, the mechanism for the high ordering temperature were not clear. So far, CuO is the only binary compound that has been found to be multiferroic [3]. CuO undergoes two successsive magnetic phase transitions upon cooling from room temperature to near zero temperature. Neutron scattering experiments [4] show that below T N 1 =213 K, the spin structure is collinear antiferromagnetic (AFM1) [see Fig. 1(a)]. Between T N 1 and T N 2 =230 K, the spin structure becomes non-collinear and slightly incommensurate (AFM2) [see Fig. 1(b)], with a modulation vector of Q= (0.006, 0, 0.017). Remarkably, an electric polarization of 160 µC·m −2 , which can be reversed by applying an electric field of about 55 kV/m, develops in the AFM2 phase. The electric polarization was attributed to the spiral spin structure [3,5] which was assumed to result from spin frustration and whereas the high ordering * Email address: helx@ustc.edu.cn temperature is believed to come from the strong exchange interactions [3].To clarify the mechanism behind its high ordering temperature and the origin of its ferroelectricity, we carry out first-principles studies of the multiferroism of CuO. We find ...

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Section: −5åmentioning

confidence: 69%

Origin of Ferroelectricity in High-TcMagnetic Ferroelectric CuO

et al. 2012

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“…This indicates that the inverse DzyaloshinskiiMoriya (DM) interaction, ∼e i j ×(S i ×S j ), contributes only 1 nC/cm 2 (<1%) to the net polarization. Thus, the exchangestriction mechanism of a (S i ·S j ) type is the origin of the magnetically induced polarization in o-TMO [11][12][13][14].…”

Section: Resultsmentioning

confidence: 98%

“…reported the magnetostructural phase diagram of o-TMO as a function of temperature and * jhlee.david@gmail.com † hmjang@postech.ac.kr magnetic field by using neutron diffraction measurements. The ground-state structural, electronic, and magnetic properties of o-TMO were subsequently investigated by employing first-principles density-functional theory (DFT) calculations [11][12][13][14]. These ab initio studies confirmed that the groundstate structural symmetry of o-TMO is P b2 1 m and the ferroelectricity in o-TMO is driven by the nearly collinear spin ordering that breaks the centrosymmetry without invoking the spin-orbit coupling.…”

Section: Introductionmentioning

confidence: 90%

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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“…[18]. The major difference between the current model and previous ones [17,18] is that we include here the single ion easy axis anisotropy K 3 for Mn 3+ ions and the easy plane anisotropies D i for Mn…”

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confidence: 93%

Molecular-spin dynamics study of electromagnons in multiferroic RMn₂O₅

Cao¹,

Guo²,

He³

2012

J. Phys.: Condens. Matter

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We investigate the electromagnon in magnetoferroelectrics RMn2O5 using combined molecularspin dynamics simulations. We identify the origin of the electromagnon modes observed in the optical spectra and reproduce the most salient features of the electromagnon in these compounds. We find that the electromagnon frequencies are very sensitive to the magnetic wave vector along the a direction. We further investigate the electromagnon in magnetic field. Although the modes frequencies change significant under magnetic field, the static dielectric constant electromagnon does not change much in the magnetic field.PACS numbers: 75.85.+t, 77.80.-e, 63.20.-e Magnetoferrelectrics with strong magnetoelectric (ME) couplings have attracted intensive attention for their novel physics [1][2][3][4] and potential applications in tunable multifunctional devices [5,6]. One of the most attractive features of the magnetoferroelectrics is that the spin waves and infrared phonons could couple via ME interactions leading to a new type of elementary excitation, electromagnon [7]. Electromagnon has mixed characters of both magnons and infrared phonons. It therefore opens a way to control the magnetic excitations via electric fields [8], which may have important applications for information processes. However, despite electromagnon has been proposed theoretically almost four decades ago, it has been observed experimentally only very recently [9]. Till today, our knowledge about electromagnon is still very limited.In the past few years, electromagnon has been observed in various magnetoferroelectrics, mostly in the family of RMnO 3 [9, 10] and RMn 2 O 5 [11] (R =Tb, Dy, Gd, Eu, Y) compounds. So far, most theoretical works on electromagnon were concentrated on the RMnO 3 family[12-14], because they have relatively simpler magnetic structures, containing only Mn 3+ ions. The study of electromagnon in RMn 2 O 5 is still very few both experimentally [11,15] and theoretically [16], due to the complexity of the magnetic structures in these compounds. A simulation of the electromagnon in RMn 2 O 5 at atomistic level is still lack. It has been shown experimentally that the dielectric step at the commensurate (CM) to incommensurate (ICM) magnetic phase transition in RMn 2 O 5 is caused by the electromagnon [11]. However, it is still unclear how the electromagnon is related to the magnetodielectric effect, which also happens at the same temperature and is one of the most prominent effects in these materials [1].In this work, we carry out combined molecular-spin dynamics(MSD) simulations to study electromagnons in RMn 2 O 5 . We reproduce the most salient features of the electromagnon in these compounds and find that the electromagnons frequencies are very sensitive to the magnetic wave vector along the a direction. We further investigate the behavior of electromagnon under magnetic fields, and find that although the mode frequency change significant under magnetic field, the static dielectric constant electromagnon does not change much in the magnet...

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First-Principles Modeling of MultiferroicRMn2O5

Cited by 63 publications

References 27 publications

Origin of Ferroelectricity in High-TcMagnetic Ferroelectric CuO

Origin of Ferroelectricity in High-TcMagnetic Ferroelectric CuO

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

Molecular-spin dynamics study of electromagnons in multiferroic RMn₂O₅

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First-Principles Modeling of MultiferroicRMn2O5

Cited by 63 publications

References 27 publications

Origin of Ferroelectricity in High-TcMagnetic Ferroelectric CuO

Origin of Ferroelectricity in High-TcMagnetic Ferroelectric CuO

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

Molecular-spin dynamics study of electromagnons in multiferroic RMn2O5

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Product

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Molecular-spin dynamics study of electromagnons in multiferroic RMn₂O₅