Tuning the electrical properties of La0.75Ca0.25MnO3 thin films by ferroelectric polarization, ferroelectric-field effect, and converse piezoelectric effect

Thin films of La0.75Ca0.25MnO3 (LCMO) have been grown on ferroelectric (1-x)Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) (x similar to 0.33) single-crystal substrates. The ferroelectric polarization in the PMN-PT substrates gives rise to a decrease in resistance and an upward shift in Curie temperature of the LCMO films, which was interpreted in terms of the ferroelectric polarization induced lattice strain effect. The resistance of the LCMO films can be modulated by applying dc/ac electric fields across the polarized PMN-PT substrates. The electric field induces lattice strains in the PMN-PT substrates via the converse piezoelectric effect, which subsequently changes the strain state and resistance of the LCMO films. A quantitative relation between the resistance in the LCMO films and the induced lattice strains in the PMN-PT substrates has been established. Moreover, we identified that the ferroelectric polarization and converse piezoelectric effect induced lattice strain effects dominate over the field effect in the LCMO/PMN-PT systems.