Effect of grain boundary on electrical, magnetic and magnetoresistance properties in La2/3Ca1/3MnO3/CuMn2O4 composites

Composites of La2/3Ca1/3MnO3 (LCMO)/ CuMn2O4 were synthesized through a sol-gel method. The effect of ferrimagnetic semiconducting CuMn2O4 on electrical and magnetic properties has been investigated in detail. The structure analysis shows CuMn2O4 mainly segregates at the grain boundaries of LCMO. With the increasing content of CuMn2O4, the electrical transport behavior turns from T2T2 dependent to T3T3 dependent at low temperatures, which suggests electron–phonon and electron–magnon scattering are becoming more important. In addition, the suppression of magnetization and magnetic transition demonstrates the magnetic coupling has a sizeable influence on the composites. A significant enhancement in magnetoresistance (MR) under an applied field 0.3 T is observed over a wide temperature range, which is considered to arise from the enhanced spin-polarized tunneling caused by the addition of CuMn2O4 at the grain boundaries.