  Complex oxides with tunable structures have many fascinating properties,
though high-quality complex oxide epitaxy with precisely controlled composition
is still out of reach. Here we have successfully developed solution-based
single crystalline epitaxy for multiferroic
(1-x)BiTi(1-y)/2FeyMg(1-y)/2O3-(x)CaTiO3 (BTFM-CTO) solid solution in large
area, confirming its ferroelectricity at atomic-scale with a spontaneous
polarization of 79~89uC/cm2. Careful compositional tuning leads to a bulk
magnetization of ~0.07uB/Fe at room temperature, enabling magnetically induced
polarization switching exhibiting a large magnetoelectric coefficient of
2.7-3.0X10-7s/m. This work demonstrates the great potential of solution
processing in large-scale complex oxide epitaxy and establishes novel
room-temperature magnetoelectric coupling in epitaxial BTFM-CTO film, making it
possible to explore a much wider space of composition, phase, and structure
that can be easily scaled up for industrial applications.
