Improper magnetic ferroelectricity of nearly pure electronic nature in cycloidal spiral CaMn${}_7$O${}_{12}$

Abstract

The noncollinear cycloidal magnetic order breaks the inversion symmetry in CaMn${}_7$O${}_{12}$, generating one of the largest spin-orbit driven ferroelectric polarizations measured to date. In this Letter, the microscopic origin of the polarization, including its direction, charge density redistribution, magnetic exchange interactions, and its coupling to the spin helicity, is explored via first principles calculations. The Berry phase computed polarization exhibits almost pure electronic behavior, as the Mn displacements are negligible, $\approx$~0.7~m\textrmÅ. The polarization magnitude and direction are both determined by the Mn spin current, where the \emph{p}-\emph{d} orbital mixing is driven by the inequivalent exchange interactions within the \emph{B}-site Mn cycloidal spiral chains along each Cartesian direction. We employ the generalized spin-current model with Heisenberg-exchange Dzyaloshinskii-Moriya interaction energetics to provide insight into the underlying physics of this spin-driven polarization. Persistent electronic polarization induced by helical spin order in nearly inversion-symmetric ionic crystal lattices suggests opportunities for ultrafast magnetoelectric response.

15 pages, 3 figures

References in corpus (20)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Spin current and magneto-electric effect in non-collinear magnets
• Magnetically driven ferroelectric order in Ni${}_3$V${}_2$O${}_8$
• Ferroelectricity in the Magnetic E-Phase of Orthorhombic Perovskites
• Ferroelectric polarization flop in a frustrated magnet MnWO${}_4$ induced by magnetic fields
• Spin-driven ferroelectricity and possible antiferroelectricity in triangular lattice antiferromagnets ACrO2 (A = Cu, Ag, Li, or Na)
• Dual nature of improper ferroelectricity in a magnetoelectric multiferroic
• Direct transition from a disordered to a multiferroic phase on a triangular lattice
• Spin-Orbit Coupling and Ion Displacements in Multiferroic TbMnO3
• Giant Ferroelectric Polarization of CaMn7O12 Induced by a Combined Effect of Dzyaloshinskii-Moriya Interaction and Exchange Striction
• The importance of anisotropic Coulomb interactions and exchange to the band gap and antiferromagnetism of β-MnO2 from DFT+U
• The importance of anisotropic Coulomb interaction in LaMnO${}_3$
• Dzyaloshinskii-Moriya interaction and spin re-orientation transition in the frustrated kagome lattice antiferromagnet
• Orbital Ordering and Magnetic Interactions in BiMnO${}_3$
• Modulated spin helicity stabilized by incommensurate orbital density waves in a quadruple perovskite manganite
• Ferroelectricity due to orbital ordering in E-type undoped rare-earth manganites
• Origin of Multiferroicity in MnWO4
• First-principles study of structurally modulated multiferroic CaMn${}_7$O${}_{12}$

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