Phase transformations and magnetic structure of nanocrystalline Fe-Pd and Co-Pt alloys studied by in situ neutron powder diffraction

摘要

The formation of the ordered L1_0 structure from the A phase in nanocrystalline Fe_(100-x)Pd_x (x =50-60) and Co_(100-x)Pt_x (x=45-55) alloys is followed by in situ neutron powder diffraction. The A1→ L1_0 transformation starts at about 620 and 730 K in Fe_(50)Pd_(50) and Co_(50)Pt_(50), respectively, and proceeds faster in the Fe-Pd alloys. In both Fe-Pd and Co-Pt, a deviation from the equiatomic composition leads to the deceleration of the ordering process. The magnetic moment of iron in the L1_0 FePd phase decreases with increasing Fe concentration from 33μ_B in Fe_(40)Pd_(60) to 3.0μ_B in Fe_(50)Pd_(50). In the Co-Pt alloys, the Co magnetic moment is found to be independent of the composition and degree of chemical order and is equal to 1.9μ_B.