Evidence of substrate induced charge order quenching, insulator metal transition, and colossal magnetoresistance in polycrystalline Pr_(0.58)Ca_(0.42)MnO_3 thin films

摘要

We report the magnetoelectrical properties of polycrystalline Pr_(0.58)Ca_(0.42)MnO_3 thin films (thickness ～ 300 nm) deposited on single crystal LaAlO_3 (LAO) and SrTiO_3 (STO) substrates. The films on LAO show charge ordering (CO) at T_(CO)≈ 240 K, with a metamagnetic ground state akin to the cluster glass (CG). In PCMO/STO films the CO is quenched and enhanced magnetic moment in the CG state suggests stronger ferromagnetic component. The resistivity of the films on LAO and STO differ drastically, the former has temperature dependence typical to the CO state, while the later show thermal cycling dependent insulator-metal transition (IMT). The large hysteresis in the temperature dependent resistivity provides the evidence of cluster coexistence. The films on STO also exhibit colossal magnetoresistance (CMR～91%) at moderate magnetic field (～10 kOe). The CO quenching, IMT, and CMR are explained in terms of the substrate induced magnetoelectrical phase coexistence.