Magnetism of diluted Co3O4 nanocrystals

An assembly of Co3O4 nanocrystals dispersed in an amorphous silicate was prepared by calcination of molecular sieve soaked in precursor solution with the concentration of 0.1 mol/l. We observed the disappearance of antiferromagnetic phase transition at 33 K of bulk Co3O4, and frequency dependence of the cusp temperature below 30 K in the AC susceptibility measurement. Divergent peaks at around 18 and 22 K were observed in the nonlinear susceptibility measurement, implying that the sample is in the spin-glass phase. The magnetic interparticle interactions were collective for the Co3O4 nanocrystals dispersed in nonmagnetic silicate.