Dynamically enhanced magnetodielectric effect and magnetic-field-controlled electric relaxations in La-doped BiMnO3

Abstract

Bi ions of multiferroic BiMnO3 were replaced with La ions in order to induce an overlap of the ferroelectric and ferromagnetic transitions in temperature and thus enhance the interproperty coupling. Twenty percent La-doped BiMnO3 in thin-film form shows a broad ferroelectric transition below 150 K; spontaneous magnetization also develops in the transition region. The saturation magnetization and polarization reach 1.6 mu(B)/Mn and 12 mu C/cm(2) at 5 K, respectively. This new magnetic ferroelectric shows a greatly enhanced magnetodielectric effect in the transition region with maximum 45% at 9 T, which is a 70-fold increase compared to that of the pure bulk compound. It is demonstrated that the magnetodielectric effect is dynamically enhanced due to a phenomenon of magnetic-field controlled electric relaxations.