SHORT-RANGE ORDER IN NI-PT ALLOYS

Electron and x-ray diffraction patterns were taken from four different Ni1-xPtx alloys, with x = 0.25. 0.35, 0.44 and 0.50, to understand th e existence and shape of the diffuse intensity, which gives us informa tion about structural fluctuations. A peculiar shape of diffuse scatte ring has been observed at 100 and 110 and their equivalent positions i n the patterns, the shape of the diffuse intensity at the 100 position changing with Pt content in the alloys. The shape of the diffuse inte nsity at the 100 position for the x = 0.25 alloy is rod-like, but the shape is nearly spherical for the x = 0.50 alloy. The x-ray diffuse sc attering intensities were measured from the x = 0.50 single-crystal al loy at room temperature, and the Warren-Cowley short-range order param eters were determined after analysing the data. The correlation length has been deduced to be about 19 Angstrom from estimating the inverse of the full width at half-maximum of the diffuse peak.