Crystal Growth, Transport, and the Structural and Magnetic Properties of Ln₄FeGa₁₂ with Ln= Y, Tb, Dy, Ho, and Er


Ln4FeGa12, where Ln is Y, Tb, Dy, Ho, and Er, prepared by flux growth, crystallize with the cubic Y4PdGa 12 structure with the Im3m space group and with a ≃ 8.5650(4), 8.5610(4), 8.5350(3), 8.5080(3), and 8.4760(3) Å, respectively. The crystal structure consists of an iron-gallium octahedra and face-sharing rare-earth cuboctahedra of the Au3Cu type. Er4Fe 0.67Ga12 is iron-deficient, leading to a distortion of the octahedral and cuboctahedral environments due to the splitting of the Ga2 site into Ga2 and Ga3 sites. Further, interstitial octahedral sites that are unoccupied in Ln4FeGa12 (Ln = Y, Tb, Dy, and Ho) are partially occupied by Fe2. Y4FeGa12 exhibits weak itinerant ferromagnetism below 36 K. In contrast, Tb4FeGa 12, Dy4FeGa12, Ho4FeGa12, and Er4Fe0;67Ga12 order antiferromagnetically with maxima in the molar magnetic susceptibilities at 26,18.5,9, and 6 K. All of the compounds exhibit metallic electric resistivity, and their iron-57 Mössbauer spectra, obtained between 4.2 and 295 K, exhibit a single-line absorption with a 4.2 K isomer shift of ca. 0.50 mm/s, a shift that is characteristic of iron in an iron-gallium intermetallic compound. A small but significant broadening In the spectral absorption line width is observed for Y4FeGa12 below 40 K and results from the small hyperfine field arising from its spin-polarized itinerant electrons © 2009 American Chemical Society.



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