Structure, Magnetic Properties and Defects Distribution of Mn0.5Zn0.5LaxFe2-xO4 Nanocrystals

La-substitution Mn-Zn ferrite nanocrystals, Mn0.5Zn0.5LaxFe2-xO4 (x=0.00, 0.05, 0.10, 0.15, 0.20) were prepared by sot-gel process. X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and positron annihilation lifetime spectroscopy (PALS) studies were carried out. The result of XRD suggests that the mean grain size decreases from 63.8 nm to 44.6 nm with the increment of La-substitution concentration from x=0.00 to 0.20. The VSM measurement shows that the saturation magnetization (MS) increases in the range of x<0.10, then it drastically decreases in the range of 0.10<x<0.20. At last, defects property is discussed using PALS.