Modulation of metal-insulator transitions in La 0.8 Ca 0.2 MnO 3 /0.7Pb(Mg 1/3 Nb 2/3 )O 3 -0.3PbTiO 3 heterostructures by electric fields

We have deposited La0.8Ca0.2MnO3 (LCMO) thin films onto a 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single-crystal substrate to construct field effect devices and investigated the electric-field–induced strain and polarization effects on the structure, magnetic, and transport properties of LCMO films. LCMO not only exhibits the usual insulator-metal transition associated with the onset of ferromagnetic state, but also a lower-temperature metal-insulator transition due to charge/orbital order. Especially, the latter transition can be modulated reversely and continuously by electric fields, leading to a large electroresistance in LCMO films (ΔR/R(0) of ~70% at 50 K). Such phenomenon could be explained based on the coactions of the piezoelectric effect and the ferroelectric-field polarization effect, which could ultimately tailor the strain and density of charge carriers in LCMO films.