Unexpectedly Large Electronic Contribution to Linear Magnetoelectricity

Bousquet, Éric; Spaldin, Nicola A.; Delaney, Kris T.

doi:10.1103/physrevlett.106.107202

Cited by 75 publications

(92 citation statements)

References 26 publications

(21 reference statements)

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“…We find a linear evolution of the polarization for B x between -25 and 25 T and ME response values: α xx = −16 ps.m −1 at η = 3.3% and −12 ps.m −1 at η = 4.5%. These values are large compared with the prototypical ME compound Cr 2 O 3 where the calculated ME response is 1.45 ps.m −1 [11]. In addition to the polarization induced along the x direction, we also observe a change in the FE polarization along the z direction even if the field is applied along the x direction.…”

Section: Fig 1 Multiferroic Phase Diagram Ofmentioning

confidence: 65%

“…However, such analysis does not allow us to predict the amplitude of the response. To determine the amplitude of the ME response, we performed calculations under a Zeeman magnetic field along the x, y and z directions and calculated the induced electric polarization [11]. In Fig.…”

Section: Fig 1 Multiferroic Phase Diagram Ofmentioning

confidence: 99%

“…To compute the ME responses, we applied a Zeeman magnetic field to the spins with the spin-orbit coupling included and extracted the polarization response as described in Ref. 11.…”

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confidence: 99%

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Induced Magnetoelectric Response inPnmaPerovskites

Bousquet

Spaldin

2011

Phys. Rev. Lett.

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We use symmetry analysis to show that the G, C and A-type antiferromagnetic P nma perovskites can exhibit magnetoelectric (ME) responses when a ferroelectric instability is induced with epitaxial strain. Using first-principles calculations we compute the values of the allowed ME response in strained CaMnO3 as a model system. Our results show that large linear and non-linear ME responses are present and can diverge when close to the ferroelectric phase transition. By decomposing the electronic and ionic contributions, we explore the detailed mechanism of the ME response.Interest in magnetoelectric (ME) materials has increased over the last few years because of their cross coupling between the electric polarization and magnetization and their consequent potential for technological applications [1]. However, the search for good MEs is facing difficulties: compounds with the required symmetry (breaking of both the time and space inversion) are uncommon, and when these requirements are met, it is often at low temperatures. In addition, although the magnitude of the response is in principle bounded by the product of the dielectric and magnetic permeabilities (α ≤ √ µ), in practice it tends to be much smaller than this value. One promising direction in the search for improved magnetoelectrics is the exploration of multiferroic materials, since the presence of multiple ferroic orders often presents the desired coupling properties for large ME responses [1][2][3]. Another route is the engineering of artificial heterostructures with specific chemistries and symmetries [4][5][6]. Here we demonstrate from symmetry considerations that the P nma G, C or A-type antiferromagnetic perovskites, which are not multiferroic and do not allow a ME response in their bulk form, can become ME when a polar distortion is induced using thin film heteroepitaxial strain. Then, using first-principles calculations for a model example -P nma CaMnO 3 -we show that particularly large ME responses can be achieved in the vicinity of the ferroelectric phase transition.Technical details-We performed all calculations within density functional theory as implemented in the VASP code [7,8]. Since the purpose of the present study is to provide a model example, we restricted ourselves to the Local Density Approximation (LDA) functional and intentionally avoided studying the U and J dependence of the LDA+U functional [9]. We oriented the P nma unit cell with the longest axis along the b direction, and applied a cubic epitaxial strain on the a and c directions by imposing a = c and relaxing the b direction. To compare with previous studies on strained CaMnO 3 [10], we performed all calculations at the calculated generalised gradient approximation (GGA) PBEsol volumes for each strain (see Supplemental Information). The non-collinear properties and the ME response were well converged at a plane wave cutoff of 550 eV and a 4×2×4 k-point grid. To compute the ME responses, we applied a Zeeman magnetic field to the spins with the spin-orbit coupling included and ex...

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Section: Fig 1 Multiferroic Phase Diagram Ofmentioning

confidence: 65%

Section: Fig 1 Multiferroic Phase Diagram Ofmentioning

confidence: 99%

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Induced Magnetoelectric Response inPnmaPerovskites

Bousquet

Spaldin

2011

Phys. Rev. Lett.

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“…As an alternative to the previous linear-response approach, Bousquet et al [43] proposed to access the magneto-electric coefficients from calculations of the change of macroscopic polarization in a finite magnetic field. In their work, the authors proposed to include the effect of the magnetic field through adding a Zeeman term ∆V Zeeman (applied on spins only) to the external potential V ext with the following expression in the 2 × 2 representation for non-collinear magnetism:…”

Section: Computing the Magnetoelectric Coefficientsmentioning

confidence: 99%

Novel magneto-electric multiferroics from first-principles calculations

Varignon

Bristowe

Bousquet

et al. 2015

Comptes Rendus. Physique

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Interest in first-principles calculations within the multiferroic community has been rapidly on the rise over the last decade. Initially considered as a powerful support to explain experimentally observed behaviours, the trend has evolved and, nowadays, density functional theory calculations has become also an essential predicting tool for identifying original rules to achieve multiferroism and design new magneto-electric compounds. This chapter aims to highlight the key advances in the field of multiferroics for which first-principles methods have contributed significantly. The essential theoretical developments that made this search possible are also briefly presented.To cite this article: J. Varignon, N. C. Bristowe, E. Bousquet and Ph. Ghosez, C. R. Physique # (2014). RésuméNouveaux matériaux multiferroïques à partir de calculs de premiers principes.L'intérêt pour les calculs ab initio dans la communauté des multiferroïques n'a cessé de croître au cours de la dernière décennie. Initialement considérés comme un support efficace pour expliquer les comportements observés expérimentalement, la tendance a évolué et, actuellement, les calculs réalisés dans le cadre de la théorie de la fonctionnelle de la densité apparaissent aussi comme un outil prédictif incontournable permettant d'identifier de nouvelles voies pour parvenir au multiferroïsme et créer de nouveaux matériaux magnéto-électriques. Ce chapitre vise à présenter quelques avancées clefs dans le domaine des multiferroïques, auxquelles les méthodes ab initio ont conbribué de manière significative. Les développements théoriques essentiels ayant permis ces avancées sont aussi brièvement discutés.

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“…1,2 The spin contribution to the ME response (from both electronic and lattice degrees of freedom) has been thoroughly studied with well established theoretical methods in typical magnetoelectrics such as Cr 2 O 3 . [3][4][5][6] On the other hand, the orbital ME response is theoretically more challenging and intriguing. It has been shown that the frozen-ion orbital ME coupling consists of two terms.…”

Section: Introductionmentioning

confidence: 99%

Gauge-discontinuity contributions to Chern-Simons orbital magnetoelectric coupling

Liu

Vanderbilt

2015

Phys. Rev. B

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We propose a new method for calculating the Chern-Simons orbital magnetoelectric coupling, conventionally parametrized in terms of a phase angle θ. According to previous theories, θ can be expressed as a 3D Brillouinzone integral of the Chern-Simons 3-form defined in terms of the occupied Bloch functions. Such an expression is valid only if a smooth and periodic gauge has been chosen in the entire Brillouin zone, and even then, convergence with respect to the k-space mesh density can be difficult to obtain. In order to solve this problem, we propose to relax the periodicity condition in one direction (say, the kz direction) so that a gauge discontinuity is introduced on a 2D k plane normal to kz. The total θ response then has contributions from both the integral of the Chern-Simons 3-form over the 3D bulk BZ and the gauge discontinuity expressed as a 2D integral over the k plane. Sometimes the boundary plane may be further divided into subregions by 1D "vortex loops" which make a third kind of contribution to the total θ, expressed as a combination of Berry phases around the vortex loops. The total θ thus consists of three terms which can be expressed as integrals over 3D, 2D and 1D manifolds. When time-reversal symmetry is present and the gauge in the bulk BZ is chosen to respect this symmetry, both the 3D and 2D integrals vanish; the entire contribution then comes from the vortex-loop integral, which is either 0 or π corresponding to the Z2 classification of 3D time-reversal invariant insulators. We demonstrate our method by applying it to the Fu-Kane-Mele model with an applied staggered Zeeman field.

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Unexpectedly Large Electronic Contribution to Linear Magnetoelectricity

Cited by 75 publications

References 26 publications

Induced Magnetoelectric Response inPnmaPerovskites

Induced Magnetoelectric Response inPnmaPerovskites

Novel magneto-electric multiferroics from first-principles calculations

Gauge-discontinuity contributions to Chern-Simons orbital magnetoelectric coupling

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