Dynamic magnetoelectric effect of the polar magnet CaBaCo4O7

We have investigated the temperature and magnetic field dependence of the dynamic magnetoelectric coefficient αE of the polar magnet CaBaCo4O7. The temperature dependence of αE exhibits a peak at the magnetic transition temperature TC in zero magnetic field, evidencing an enhanced magnetoelectric effect near the phase boundary. When a DC magnetic field is applied along either a- or b-axis, the peak position of αE shifts continuously to a higher temperature while the peak amplitude reaches the maximum at a critical field and decays for higher magnetic fields. The obtained magnetoelectric phase diagram suggests that the maximum dynamic magnetoelectric effect occurs in a region above TC where short-range magnetic correlations play a crucial role and the peak is due to a metamagnetic transition. The measurements of the magnetostrictive coefficient dλ/dH reveal that the magnetoelectric effect is closely related to the magnetoelastic coupling. Our study provides insights toward achieving significant dynamic magnetoelectric effect at high temperatures in polar magnets.