Modulation of metal-insulator transitions in La_0.8Ca_0.2MnO₃/0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ heterostructures by electric fields

¹ Department of Physics, the University of Hong Kong - Pokfulam Road, Hong Kong
² College of Physics and Electronic Information Science, Tianjin Normal University - Tianjin 300074, China

^a jugao@hku.hk

Received: 26 May 2011
Accepted: 12 July 2011

Abstract

We have deposited La_0.8Ca_0.2MnO₃ (LCMO) thin films onto a 0.7Pb(Mg_1/3Nb_2/3)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.