Effect of Film Thickness on Electrical and Magnetic Properties of Nd0.8Na0 .2MnO3 Thin Films

Nd0.8Na0.2MnO3 thin films were grown on (001)-oriented LaAlO3 substrate for thickness in the range of 30 to 100 nm by using radio-frequency (RF) magnetron sputtering. All films are found to grow epitaxially along the (001) orientation of the substrate. The out-of-plane lattice constant is found to decrease from 3.862 for 30 nm thick film to 3.853 for 100 nm film. These films exhibit out-of-plane tensile strain and their magnitude is found to decrease with an increase in film thickness. The Raman spectra show the signature of the presence of a charge ordered phase. The temperature variation of magnetization measurement shows the signature of charge ordering transition around 190 K followed by low temperature (T < 100 K) ferromagnetic transition. The M-H loops recorded at 30 K show typical ferromagnetic behaviour with a maximum saturation magnetization of 2.47 mu (B)/f.u. The electrical resistivity data are found to follow the variable range hopping model.