Giant magnetostriction and nonsaturating electric polarization up to 60 T in the polar magnet CaBaCo_4O_7

摘要

Giant magnetostriction in insulating magnetic materials is highly required for applications but is rarely observed. Here we show that giant magnetostriction (>l500ppm) can be achieved in an insulating transition metal oxide CaBaCo_4O_7 where the ferrimagnetic ordering at T_C ～ 62 K is associated with a huge change in the lattice. Moreover, because this material is pyroelectric with a nonswitchable electric polarization (P), the giant magnetostriction results in a pronounced magnetoelectric effect-a huge change of electric polarization (AP～ 1.6μC/cm~2) in response to the applied magnetic field up to 60 T. Geometric frustration as well as the orbital instability of Co~(2+) /Co~(3+) ions is believed to play a crucial role in the giant magnetostriction. Our study provides insights on how to achieve both giant magnetostriction and pronounced magnetoelectric effect in insulating transition metal oxides.