Doping effect on ferroelectric microstructure in YMn1-xTixO3

We have investigated microstructures related to anomalous ferroelectric propel-ties such as the magnetocapacitance effect in magnetic ferroelectric compounds YMn1-xTixO3 and (Y,A)Mn0.825Ti0.175O3 (A = La, Ca, Zr) mainly by the transmission electron microscopy. It is found that the size of the ferroelectric domains in YMn1-xTixO3 depends strongly on the Ti concentration (x) and the size is estimated to be about 10-20 nm in the x = 0.175 compound. In addition, structural change from the ferroelectric P6(3) cm phase to the rhombohedral one was found in the x = 0.40 compound. On the other hand, characteristic diffuse scattering elongating along both the [001] and [110] direction was found in (Y,Zr)Mn0.825Ti0.175O3, which is similar to that found in the x = 0.175 compound. It is revealed that the partial substitution in YMnO3 breaks the long-ranged FE ordering and structural fluctuation is induced, which should be responsible for the anomalous FE behaviors in these compounds.