Electrical transport and magnetic properties of epitaxial [formula omitted] thin films on (001)-oriented LaAlO3 substrate

Abstract

Nd0.7Sr0.3MnO3 thin films were deposited using RF-magnetron sputtering on (001) oriented LaAlO3 substrate by varying thickness in the range of 12–200nm. X-ray diffraction patterns of both air annealed and oxygen annealed films show epitaxial growth along (00l) orientation with decrease in lattice strain with increase in film thickness. Raman spectra show the presence of strong peaks corresponding to rotational and stretching modes of MnO6 octahedra and their intensity is found to decrease with increase in film thickness. Both air and oxygen annealed films except for 12nm thickness exhibit ferromagnetic transition with a maximum TC of 200K. The magnetic anisotropic constant was estimated from the analysis of M–H curve and its value is found to decrease with increase in film thickness. Metal-insulator transitions have been observed in all films including the 12nm thick film. The electrical resistivity data in the metallic region, i.e. close to TMI, were analysed by considering electron–magnon scattering mechanism and in the low temperature region far below TMI; the analysis was carried out by considering the combination of electron–electron scattering and charge localisation effect. The resistivity data in the insulating region (T>TMI) were analysed by considering Mott-variable range hopping model.