Study of Electrical Transport and Magnetic Properties of Nd0.7Sr0.3MnO3/Nd0.8Na0.2MnO3 Bilayer Thin Films

Abstract

Bilayer films of Nd0.7Sr0.3MnO3/Nd0.8Na0.2 MnO3 were grown on 001-orientated LaAlO3 substrate by using RF magnetron sputtering. The thickness of the Nd0.8Na0.2MnO3 (NNMO) film was kept fixed at 120 nm while that of the Nd0.7Sr0.3MnO3 (NSMO) film was varied from 12 to 100 nm. X-ray diffraction patterns confirm the growth of films along the (001) direction, and the out-of-plane lattice constant of the NSMO film decreases with an increase in film thickness. The bilayer films are found to undergo out-of-plane tensile strain, and the lattice strain is found to decrease with an increase in film thickness. The ferromagnetic transition temperature is found to increase with an increase in the NSMO film thickness. M–H loops recorded at 50 K show a systematic increase in saturation magnetisation with an increase in film thickness. Metal–insulator transition has been observed for the film thickness of 30 nm and above, and the transition temperature is found to increase with an increase in film thickness. The electrical resistivity data in the metallic region were explained based on electron–electron and electron–magnon scattering mechanism by including a weak localisation effect at low temperature. The electrical resistivity data in the insulating region follow the Mott-variable range hopping model.