Size-induced transition from non–Griffiths-like to Griffiths-like clustered phase above the Curie temperature
Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China Hefei, Anhui 230026, PRC
Accepted: 11 May 2012
Recent studies on several pervoskite oxides such as Sm0.5Sr0.5MnO3, La0.7Sr0.3CoO3, and La2NiMnO6, reveal that their inverse susceptibilities exhibit an upward deviation from Curie-Weiss behavior above TC, indicating the existence of a non–Griffiths-like clustered phase due to the dominance of antiferromagnetic interactions in this regime. Here, we study the magnetic behaviors of their nanoparticles and find that the deviation becomes sharply downward, which is a typical characteristic of a Griffiths-like phase. This suggests that reducing the particle size induces a phase transition from non–Griffiths-like to Griffiths-like. We propose that the weakening of the antiferromagnetic interactions by size reduction is responsible for this transition.
PACS: 75.47.Lx – Magnetic oxides / 75.40.-s – Critical-point effects, specific heats, short-range order / 75.50.Tt – Fine-particle systems; nanocrystalline materials
© EPLA, 2012