Magnetoelectric emission in a magnetic ferroelectric Er-doped $(Ba,Sr)TiO3$

As the system where both space-inversion and time-reversal symmetries are broken simultaneously, the authors have investigated an $Er3+$-doped ferroelectric $(Ba,Sr)TiO3$ single crystal under magnetic field, in which the luminescent magnetic $Er3+$ ion occupies a noncentrosymmetric site. The $k$-directional dichroism, termed the optical magnetoelectric (OME) effect, was verified in the $I13∕24→I15∕24$ emission $(λ∼1.55μm)$ by the reversal of magnetic field and spontaneous polarization. The observed nonreciprocity $ΔI∕I∼0.5%$ at $3000Oe$ implies the possibility of the application of the OME effect to the function of an optical isolator.