Grain size-induced structural, magnetic and magnetoresistance properties of Nd0.67Ca0.33MnO3 nanocrystalline thin films

The effects of grain size (G (S)) on the structural, magnetic and magnetoresistance properties of sol-gel-derived Nd0.67Ca0.33MnO3 (NCMO) nanocrystalline thin films were investigated. To change the G (S) of the NCMO samples, the annealing temperature (T (A)) was changed from 600 to 800 A degrees C. All the prepared samples were confirmed as hexagonal single-phased polycrystalline structure. The average nanocrystalline size and G (S) were increased with increasing T (A). The range of the G (S) was approximately 25-40, 50-65 and 75-90 nm for the NCMO samples annealed at T (A) = 600, 700 and 800 A degrees C, respectively. As the G (S) increased, the metal-insulator transition temperature, T (MI), and the paramagnetic-ferromagnetic transition temperature, T (C), also increased including the ferromagnetic response. The magnetoresistance, MR, values were found to increase with increasing the G (S) at any annealing temperature. [GRAPHICS]