Effect of Annealing in a Ferromagnetic State on the Structure of an Fe–18 at % Ga Alloy
The atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic (T > TC) and ferromagnetic (T < TC) state. In the first case, the structural state was fixed by quenching from the annealing temperature into water; in the second case, the structural state was obtained by slow cooling. The structural studies of the single-crystal samples were conducted on a four-circle X-ray diffractometer at room temperature. From the X-ray diffraction data, it follows that the alloy, independently on the heat treatment, contains B2 clusters, i.e., locally ordered regions with the CsCl-type structure observed in alloys of iron with silicon (to 10 at % Si) and aluminum (7 at % Al) before. In addition to the B2‑clusters, regions with the D03 short-range order are observed in the quenched sample; the sizes of these regions significantly increases after annealing in the ferromagnetic state, i.e., a long-range order forms. The relation of the fine structural changes in the alloy due to various heat treatments with its magnetoelastic and magnetostriction properties is discussed.
This work was carried out in the framework of the state task (the theme “Magnit” No. AAAA-A18-118020290129-5) and was supported by the program of the Ural Branch of the Russian Academy of Sciences (project no. 18-10-2-5) and the Russian Foundation for Basic Research (project no. 18-02-00391).
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