  Finite size effect on the antiferromagnetic transition temperature, TN, of
Co3O4 nanoparticles of 75, 35, and 16 nm in diameter, has been investigated.
The AFM transition point, TN, reduces with the decreasing diameter, d. Along
with the results from the previous experiments on the Co3O4 nanoparticles of 8
and 4.3 nm, the variation of TN with d appears to follow the finite size
relation. According to the scaling behavior, the shift exponent is determined
as \lambda = 1.4 \pm 0.4, the correlation length, \ksi_0 = 3.0 \pm 0.3 nm, and
the bulk Neel temperature, TN(\infint) = 38.6 \pm 0.7 K.
