A Y2O3 : Yb nanoscale magnet obtained by HEBM: C-3i/C-2 site occupancies, size/strain analysis and crystal field levels of Yb3+ ions
АуториKremenović, Aleksandar S.
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A Y2O3: Yb nanoscale magnet that belongs to the cubic C-type or bixbyite structure family was synthesized by high energy ball milling ( HEBM). An as-prepared sample ( S1) was annealed at 650 degrees C ( S2) and 950 degrees C ( S3). Cation populations were determined by the refinement of site occupancies. It was found that in S1 and S2 Yb3+ ions occupy exclusively the 8b ( or C-3i) position, whereas in S3 a small amount of Yb3+ is also located on Wyckoff-site 24d ( or C-2). X-ray powder diffraction line broadening analysis was done by using the Rietveld method using regular TCH-pV functions ( isotropic effects) and symmetrized cubic harmonics ( anisotropic effects) for the refinement. The line broadening anisotropy decreases due to strain effects from S1 to S3, while the crystallite size anisotropy increases from S1 to S3. Transmission electron microscopy ( TEM) and Raman spectroscopy were used to define the homogeneity, microstructure and to locally probe the structure of the samples S...1-S3. Magnetic susceptibility results in the 2-300 K temperature regions were analysed by applying the first-order perturbation theory. The mean energy gap between ground and excited crystal field levels ( E-i), and their effective magnetic numbers M-ieff, were determined. The analysis of the paramagnetic temperature shows the absence of clusterization of the magnetic ions.
Извор:Nanotechnology, 2007, 18, 14
ISSN: 0957-4484 (print); 1361-6528 (electronic)