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

Abstract

The formation of the ordered L 10 structure from the A1 phase in nanocrystalline Fe100-x Pdx (x=50-60) and Co100-x Ptx (x=45-55) alloys is followed by in situ neutron powder diffraction. The A1→L 10 transformation starts at about 620 and 730 K in Fe50 Pd50 and Co50 Pt50, 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 L 10 FePd phase decreases with increasing Fe concentration from 3.3 μB in Fe40 Pd60 to 3.0 μB in Fe50 Pd50. 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 1.9 μB. © 2009 American Institute of Physics.