Abstract
Extended X-ray absorption fine-structure (EXAFS) measurements were carried out on ordered and disordered Fe–Pt alloys near the γ-α phase boundary in the temperature range 20–800 K. EXAFS spectra were analyzed by the method of Fine Adjustment Based on Model (FABM) proposed by Teo et al. , in order to determine the local structure with high precision. The interatomic distance of Pt–Fe pair shows expansion below T c with decreasing temperature, which corresponds quite well to the Invar effect. In the interatomic distance of Pt–Pt pair, anomalous expansion is observed, starting from a relatively high temperature. We regard it as first direct observation on the local-structure change resulting from the premartensitic transformation. As for the local-structure change, no essential difference is recognized between the ordered and disordered Fe–Pt alloys.
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