Asymmetry induced intrinsic magnetodielectric effects in manganite - Barium titanate solid solutions

Multiferroics, in which off-center magnetic ions induced ferroelectricity, are believed to exhibit enhanced magnetoelectric (ME) or magnetodielectric (MD) effects because their ferroelectricity and ferromagnetism are driven by the same originations. In this paper, multiferroics with off-center Mn ions were obtained in hexagonal manganite-barium titanate solid solutions. As an external magnetic field (H) was applied, intermediate and high frequency MD effects were observed. The MD (MD(%) = (ε(H = 3.5 kOe) − ε(H = 0 Oe)) × 100/ε(H = 0 Oe)) values at 10 MHz frequency were 3.37%, 3.21% and 2.65% for the three samples, respectively. The further discussion indicated that the MD effects did not originate from some extrinsic source such as grain boundary magnetoresistance (MR) and contributions from the electrode, but mainly attributed to the intrinsic ME coupling such as magnetic-field-induced variations of asymmetric hopping. The first-principles calculations also confirmed that the asymmetry of coplanar octahedrons aggravated when Mn ions occupied the off-center site in the hexagonal phases, especially in 0.1La0.7Ca0.3MnO3 − 0.9BaTiO3 solid solutions.