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MM: Metall- und Materialphysik
MM 38: Nanostructured Materials II
MM 38.2: Talk
Thursday, March 30, 2006, 16:45–17:00, IFW D
Size Effect on the Néel Temperature of NiO nanoparticles — •X. M. Li, Z. Q. Guan, H. Wolf, and Th. Wichert — Technische Physik, Universität des Saarlandes, D-66041 Saarbrücken
Nanocrystalline NiO with different particle sizes has been prepared by electrochemical deposition followed by thermal treatment. The particle sizes ranged from 7 nm to 26 nm as determined by XRD and TEM. Using the method of perturbed γγ-angular correlation (PAC), the antiferromagnetic order of nanocrystalline NiO as a function of temperature was studied for different particle sizes. The results show that the Néel temperature decreases with decreasing particle size. For the Néel temperature TN as a function of the particle size d a relation of (TN(bulk)-TN(nano)) ∼ d−λ has been obtained yielding for the exponent λ = 3.45(1). A similar relation was obtained in nano-crystalline Gd for the Curie temperature as a function of the particle size by D. Michel [1]. The exponent λ = 1.07, however, is significantly smaller than that in the present case of nanocrystalline NiO.
supported by the Deutsch Forschungsgemeinschaft (SFB277).
D. Michel, Thesis, Universität des Saarlandes, Saarbrücken, Germany(2005).