LAUSR

Influence of the crystalline size on the magnetic and critical properties of Pr 0.6 Sr 0.4 MnO 3 nanocrystals has been investigated. The results show that Curie temperature ( T C ) and magnetization slightly decrease with decreasing crystalline size ( D ). Based on the mean-field theory and the magnetic-field dependences of magnetization at different temperatures M ( H , T ), we pointed out that the ferromagnetic-paramagnetic phase transition in the samples undergoes the second-order phase transition with the critical exponents ( β , γ , and δ ) close to those of the mean-field theory. However, there is a small deviation from those expected for the mean-field theory of the values of β , g , and δ obtained for the samples. It means that short-range ferromagnetic interactions are appeared in the smaller particles. In other words, Pr 0.6 Sr 0.4 MnO 3 nanocrystals become more magnetically inhomogeneous with smaller crystalline sizes that could be explained by the presence of surface-related effects, lattice strain and distortions, which lead to the strength of Mn 3+ -Mn 4+ ferromagnetic interaction decreases in the small crystallite sizes.