We report on the results of a search for the electron electric dipole moment $d_e$ using paramagnetic ferroelectric Eu$_{ 0.5}$Ba$_{ 0.5}$TiO$_3$. The electric polarization creates an effective electric field that makes it energetically favorable for the spins of the seven unpaired $4f$ electrons of the Eu$^{ 2+}$ to orient along the polarization, provided that $d_e\neq 0$. This interaction gives rise to sample magnetization, correlated with its electric polarization, and is therefore equivalent to a linear magnetoelectric effect. A SQUID magnetometer is used to search for the resulting magnetization. We obtain $d_e = (-1.07\pm3.06_\text{ stat}\pm 1.74_\text{ sys})\times10^{ -25}\ecm$, implying an upper limit of $|d_e|<6.05\times10^{ -25}\ecm$ (90% confidence).
Categories: physics.atom-ph