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  • Title: Magnetism of nanocrystalline (La(0.5)Sr(0.5))TiO3 doped with 3d cations.
    Author: Wongsaprom K, Venkatesan M, Maensiri S, Coey JM.
    Journal: J Phys Condens Matter; 2010 Mar 10; 22(9):096004. PubMed ID: 21389431.
    Abstract:
    Nanocrystallites of nominal composition (La(0.5)Sr(0.5))TiO(3) 12-15 nm in diameter exhibit a diamagnetic susceptibility that is greater by a factor of three than that of bulk ceramic material, due to a much-reduced Pauli paramagnetic contribution associated with oxidation (cation deficiency) of the material. Doping the nanocrystallites with 1.5 or 2.0% of every transition metal from V-Ni adds a Curie term to the susceptibility. Exchange coupling between these paramagnetic ions is very weak. In the cases of Fe, Co and Ni there is an additional hysteretic ferromagnetic magnetization, with a moment equivalent to a few tenths of a Bohr magneton per dopant atom, which is attributed to a secondary ferromagnetic impurity phase. Mössbauer analysis of samples prepared with (57)Fe reveals the presence of some metallic iron. Metallic nickel is detected by x-ray diffraction, but no direct evidence of metallic cobalt was found in the ferromagnetic Co-doped material. The possibility of high temperature defect-related ferromagnetism in a metallic oxide is discussed.
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