Structural studies of the phase separation of amorphousFexGe100−xalloys
| Autor: | Arthur Bienenstock, Timothy I. Morrison, R.D. Lorentz |
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| Rok vydání: | 1994 |
| Předmět: | |
| Zdroj: | Physical Review B. 49:3172-3182 |
| ISSN: | 1095-3795 0163-1829 |
| DOI: | 10.1103/physrevb.49.3172 |
| Popis: | Small-angle x-ray scattering and x-ray-absorption near-edge spectroscopy (XANES) experiments have been performed on amorphous ${\mathrm{Fe}}_{\mathit{x}}$${\mathrm{Ge}}_{100\mathrm{\ensuremath{-}}\mathit{x}}$ alloys over the composition range 0\ensuremath{\le}x\ensuremath{\le}72. The observed small-angle x-ray-scattering patterns were compared both with those calculated for a model assuming segregation of the alloys into particular phases and with scattering patterns calculated for voids in a homogeneous matrix. The x-ray-absorption near-edge-structure data were used to test for phase separation. No large-scale phase separation is observed in the semiconductor-metal transition region (15--25 at. % Fe), but fine-scale, kinetically limited phase separation or other types of composition fluctuations cannot be ruled out. The results also indicate that phase separation occurs for alloys with 37\ensuremath{\le}x\ensuremath{\le}72, with data consistent with separation into amorphous ${\mathrm{FeGe}}_{2}$ and ${\mathrm{Fe}}_{3}$Ge. Thus, ferromagnetic moment formation occurs in the phase-separated region, with the transition composition (40--43 at. % Fe) probably linked to a-${\mathrm{Fe}}_{3}$Ge percolation, as hypothesized by Janot for the related ${\mathrm{Fe}}_{\mathit{x}}$${\mathrm{Sn}}_{100\mathrm{\ensuremath{-}}\mathit{x}}$ system. This phase separation explains the Mossbauer observation of ``magnetic'' and ``nonmagnetic'' Fe atoms in these alloys. |
| Databáze: | OpenAIRE |
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