Competition between external and internal electric fields induced multiple transitions of pole and pyroelectric currents in tetracobalt diniobate

Abstract

Thermally stimulated depolarization current (TSDC) related internal electric field (Eint) is found to influence the pyrocurrent of multiferroics greatly, but its effect on the pole current of magnetoelectric (ME) materials has never been studied. In this article, ME antiferromagnet tetracobalt diniobate is cooled under an external electric field (Eext) from 125 K to generate the TSDC related Eint. Under a magnetic field (H), the pole current while cooling in the presence of Eint and Eext, and the subsequent pyrocurrent while heating without applying Eext is studied. Competition between Eext and Eint induces multiple transitions of pole current, and some transitions gradually disappear with increasing H. The pyrocurrent shows three transitions that are ascribed to the domain switching by Eint, depolarization of negative and positive domains, respectively. With increasing H, the transition at the highest temperature gradually disappears, indicating that the polarization is easier to be switched under a stronger H, which is explained both from the aspects of electrostatic potential energy and the special magnetic structure responsible for magnetoelectricity.