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Polarization-Magnetization Coupling in Visible Light Ferroelectric Double Perovskites

Sathiyamoorthy Buvaneswaran, Trilochan Sahoo, Saurabh Ghosh

Abstract

The bulk photovoltaic effect (BPVE), arising from broken inversion symmetry in ferroelectrics, offers a distinct pathway toward high-efficiency next-generation photovoltaics. We propose and investigate A/A$^\prime$-ordered double perovskites KLaFeMoO$_6$ and NaLaFeMoO$_6$ as promising single-phase ferroelectric photovoltaic (FE-PV) materials. First-principles calculations reveal robust P2$_1$ symmetry with A-site layer and B-site rock-salt ordering, accompanied by hybrid improper ferroelectricity driven by $a^{-}a^{-}c^{+}$ octahedral tilts. Both compounds exhibit significant spontaneous polarization and indirect band gaps of $\sim$ 1.8 eV, well suited for visible-light absorption ($>$10$^5$ cm$^{-1}$). Low carrier effective masses along the polar axis indicate efficient charge transport. \textit{Ab initio} molecular dynamics simulations (AIMD) show that polarization-coupled magnetization switching is feasible above room temperature, making these materials suitable for room-temperature applications.

Polarization-Magnetization Coupling in Visible Light Ferroelectric Double Perovskites

Abstract

The bulk photovoltaic effect (BPVE), arising from broken inversion symmetry in ferroelectrics, offers a distinct pathway toward high-efficiency next-generation photovoltaics. We propose and investigate A/A-ordered double perovskites KLaFeMoO and NaLaFeMoO as promising single-phase ferroelectric photovoltaic (FE-PV) materials. First-principles calculations reveal robust P2 symmetry with A-site layer and B-site rock-salt ordering, accompanied by hybrid improper ferroelectricity driven by octahedral tilts. Both compounds exhibit significant spontaneous polarization and indirect band gaps of 1.8 eV, well suited for visible-light absorption (10 cm). Low carrier effective masses along the polar axis indicate efficient charge transport. \textit{Ab initio} molecular dynamics simulations (AIMD) show that polarization-coupled magnetization switching is feasible above room temperature, making these materials suitable for room-temperature applications.

Paper Structure

This paper contains 4 figures, 1 table.

Figures (4)

  • Figure 1: Optimized $P2_1$ structure of KLaFeMoO$_6$ showing A-type AFM ordering, in which Fe spins are ferromagnetically aligned within the $ab$ plane and antiferromagnetically coupled along the $c$ axis. (b) Corresponding total DOS of KLaFeMoO$_6$.
  • Figure 2: Band dispersion of the highest VB and the lowest CB along high-symmetry directions in the Brillouin zone of KLaFeMoO$_6$, calculated using GGA+U+MBJ+SOC. Blue and red circles indicate the maxima of VB and minima of CB, respectively.
  • Figure 3: Calculated optical absorption spectrum $\alpha(\omega)$ of AA$^\prime$FeMoO$_6$ (AA$^\prime$ = KLa and NaLa), compared with conventional semiconductors GaAs and CdTe.
  • Figure 4: (a) Displacement of K and La atoms over 100 $ps$ at 400 K. Snapshot of the structure in the intermediate polarization state ($\vec{P}_{0}$). (c) Real part of the dielectric function $\epsilon_{1}(\omega)$ for the polarization states (${P_{+}}$), (${P_{0}}$) and (${P_{-}}$).