Magnetic properties of Ni:SiO2 nanocomposites synthesized by a modified sol-gel method

Ni nanoparticles embedded in an amorphous SiO2 matrix were produced by a modified sol-gel method. This method resulted in nanocomposites with a controlled size distribution and good dispersion of the metallic particles. The particle-size distributions were found to have an average radius of similar to3 nm, as inferred from transmission electron microscopy, X-ray-diffraction analysis, and magnetic measurements. Magnetic characterizations revealed that samples exhibit superparamagnetic behavior above the blocking temperature T-B, 20 K less than or equal to TB less than or equal to 40 K, and absence of a shift along the field axis on hysteresis loops measured at T less than or equal to T-B, indicating that the metallic nanoparticles are also free from an oxide layer.