Tunable low-field magnetoresistance properties in (La_0.7Ca_0.3MnO₃)_1-x:(CeO₂)_x vertically aligned nanocomposite thin films

Vertically aligned nanocomposite (VAN) (La_0.7Ca_0.3MnO₃)_1-x:(CeO₂)_x thin films have been deposited on SrTiO₃ (001) substrates by pulsed laser deposition. Enhanced low-field magnetoresistance properties and tunable metal-insulator transition temperature (T_MI) have been demonstrated via modulating the composition of (La_0.7Ca_0.3MnO₃)_1-x:(CeO₂)_x (x = 0, 0.05, 0.1, and 0.2). By increasing the atomic percentage of the CeO₂ phase to 20%, a maximum magnetoresistance value of 51.8% can be achieved and the T_MI value can be tuned from 113 K to 210 K. The enhanced magnetoresistance properties are attributed to the disordered grain boundary and tunneling structure generated by the insulating CeO₂ phase. The change in the T_MI value is attributed to the strain state in the La_0.7Ca_0.3MnO₃ phase. Furthermore, high ferromagnetic anisotropy and enhanced magnetization have been demonstrated in the VAN system. This work demonstrates the power of multifunctionalities and property tuning in VAN thin films.