NiO Nanoparticles Dispersed in Mesoporous Silica Glass

We have studied the magnetic properties of NiO nanoparticles dispersed into mesoporous silica glass with three particle size distributions obtained using the bottom-up nanofabrication technique. The samples were characterized by XRD, Raman, and TEM and found to consist of monodispersed rock salt structure NiO nanoparticles. The magnetic results indicate that the particles can be considered as an antiferromagnetically ordered core with an uncompensated magnetic moment, and a magnetically disordered surface. The magnetization loops exhibit a loop shift with intriguing temperature dependence. Furthermore, an increase in the average blocking temperature is observed with increases in the number of impregnation−decomposition cycles. These results are discussed considering the influence of the magnetic interaction on the core−shell structure of the nanoparticles.