Chemical order and structure of the mechanically milled Fe2Hf Laves phase

The effects of mechanical milling on the chemical order and structure of the Fe2Hf C14 Laves phase have been studied by x-ray diffraction and Moessbauer spectroscopy. The results show that ball milling leads to a segregation of two phases. One, with a lower degree of chemical disorder, maintains the structure of the original intermetallic phase and the other, with a higher degree of chemical disorder, exhibits a disordered structure. At 4.2 K, the two phases exhibit similar hyperfine magnetic fields which are smaller than that of the original intermetallic phase, but much larger than that of the amorphous alloy with the same composition, prepared by sputtering deposition. Differing from the crystalline phase, the structurally disordered phase shows a Curie temperature lower than room temperature. (author)