Superparamagnetism and magnetic properties of Ni nanoparticles embedded in SiO2 -: art. no. 104406

We have performed a detailed characterization of the magnetic properties of Ni nanoparticles embedded in a SiO2 amorphous matrix. A modified sol-gel method was employed which resulted in Ni particles with average radius similar to3 nm, as inferred by TEM analysis. Above the blocking temperature T(B)approximate to20 K for the most diluted sample, magnetization data show the expected scaling of the M/M-S vs H/T curves for superparamagnetic particles. The hysteresis loops were found to be symmetric about zero field axis with no shift via exchange bias, suggesting that Ni particles are free from an oxide layer. For T