Magnetocapacitance effect and related microstrucuture in Ti-doped YMnO3

We have investigated microstructures giving rise to magnetocapacitance effect in Ti-doped YMnO3 (YMn1-xTixO3) by both electron diffraction and real-space imaging techniques. Diffuse scattering elongating along the [110] direction due to the instability of the Mn trimerization were found in the x=0.175 compound, which exhibits the enhanced magnetocapacitance effect. With increasing Ti concentration, the centrosymmetric (paraelectric) R3̄c phase grows up at the expense of the ferroelectric P63cm phase around x=0.20 and the R3̄c phase is dominant above x=0.30. Our present results indicate that the Mn trimers with the short-range correlation inside the ferroelectric nanodomains with the 10-20nm size should be responsible for the enhancement of the magnetocapacitance and, on the other hand, the appearance of the R3̄c phase suppressed the magnetocapacitance effect.