Giant magnetostriction and nonsaturating electric polarization up to 60 T in the polar magnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>CaBa</mml:mi><mml:msub><mml:mi>Co</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:mrow></mml:math>
Yisheng Chai, Junzhuang Cong, Jincheng He, Dan Su, X. X. Ding, John Singleton, Vivien S. Zapf, Young Sun
Abstract
Giant magnetostriction in insulating magnetic materials is highly required for applications but is rarely observed. Here we show that giant magnetostriction $(>1500\phantom{\rule{0.16em}{0ex}}\mathrm{ppm})$ can be achieved in an insulating transition metal oxide $\mathrm{CaBa}{\mathrm{Co}}_{4}{\mathrm{O}}_{7}$ where the ferrimagnetic ordering at ${T}_{\mathrm{C}}\ensuremath{\sim}62\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ 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 $(\mathrm{\ensuremath{\Delta}}P\ensuremath{\sim}1.6\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{C}/\mathrm{c}{\mathrm{m}}^{2})$ in response to the applied magnetic field up to 60 T. Geometric frustration as well as the orbital instability of ${\mathrm{Co}}^{2+}/{\mathrm{Co}}^{3+}$ 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.