A multiferroic material to search for the permanent electric dipole moment of the electron


We describe the first-principles design and subsequent synthesis of a new material with the specific functionalities required for a solid-state-based search for the permanent electric dipole moment of the electron. We show computationally that perovskite-structure europium barium titanate should exhibit the required large and pressure-dependent ferroelectric polarization, local magnetic moments and absence of magnetic ordering at liquid-helium temperature. Subsequent synthesis and characterization of Eu0.5Ba0.5TiO3 ceramics confirm the predicted desirable properties.

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Figure 1: Illustration that an electron with an EDM violates time-reversal symmetry.
Figure 2: Schematic of the physics underlying the experiment to search for the electron EDM.
Figure 3: Calculated phonon dispersion of ferromagnetic Eu0.5Ba0.5TiO3 in its high-symmetry reference structure with pseudocubic lattice constant a0=3.95 Å.
Figure 4: Temperature dependence of permittivity and dielectric loss in Eu0.5Ba0.5TiO3 ceramics.
Figure 5: Temperature dependence of ac magnetic susceptibility, χ, at various static magnetic fields and a frequency of 214 Hz.


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This work was supported by the US National Science Foundation under award number DMR-0940420 (NAS), by Yale University, by the Czech Science Foundation (project Nos. 202/09/0682 and AVOZ10100520) and by the Young Investigators Group Programme of the Helmholtz Association, Germany, contract VH-NG-409. We thank O. Pacherova, R. Krupkova and G. Urbanova for technical assistance and O. Sushkov for discussions.

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S.K.L. supervised the EDM measurement effort at Yale. A.O.S. and S.E. carried out the analysis and made preliminary measurements, showing that these materials could be useful in an EDM experiment. M.L. and N.A.S. selected (Eu,Ba)TiO3 as the candidate material according to the experimental requirements and supervised the ab initio calculations. K.Z.R. carried out the ab initio calculations. M.L., N.A.S. and K.Z.R. analysed the ab initio results and wrote the theoretical component of the paper. Ceramics were prepared by P.V. Crystal structure was determined by K.K. and F.L. Dielectric measurements were carried out by M.S. J.P. investigated magnetic properties of ceramics. V.G. carried out infrared reflectivity studies. D.N. investigated terahertz spectra. S.K. coordinated all experimental studies and wrote the synthesis and characterization part of the manuscript. N.A.S. coordinated the preparation of the manuscript.

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Correspondence to N. A. Spaldin.

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Rushchanskii, K., Kamba, S., Goian, V. et al. A multiferroic material to search for the permanent electric dipole moment of the electron. Nature Mater 9, 649–654 (2010). https://doi.org/10.1038/nmat2799

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