Crystal size and magnetic field effects in Co3O4 antiferromagnetic nanocrystals

We report magnetism of spinel Co3O4 nanocrystals with average diameters of similar to 25 and similar to 100 nm under magnetic fields up to 50 kOe. The nanoparticles were controlled to be cubic in shape. In the smaller nanocrystal sample (d similar to 25 nm), a spontaneous magnetic moment increased steeply below the Neel point, T-N=32 K of the bulk sample, whereas similar to bulk samples the larger crystal sample (d similar to 100 nm) exhibited a maximum in magnetization around T-N. A spin-glass-like behavior in magnetization was observed at T-t=10 K at lower magnetic fields, whereas above H=30 kOe, this behavior disappeared.