Finite size effect on Ńel temperature with Co3 O4 nanoparticles

The finite size effect on the antiferromagnetic transition temperature, TN, has been investigated with Co3 O4 nanoparticles of 75, 35, and 16 nm in diameter. Along with the results from the previous experiments on the Co3 O4 nanoparticles with average diameter of 8 and 4.3 nm, the variation of TN with the particle diameter, d, appears to follow the finite size scaling relation. The shift exponent is determined as λ=1.1±0.2 and the correlation length 0 =2.8±0.3 nm. The value of the shift exponent is consistent with the description by the mean field theory.