THE MAGNETIZATION DENSITY PROFILE OF A GRAIN-BOUNDARY IN NICKEL

We report the measured atomic and magnetization densities of a nickel twist grain boundary averaged over its lateral dimensions as a functio n of distance from the interface plane. The presence of a reconstructe d interface region (the grain boundary) sandwiched between two single- crystal nickel films that were hot-pressed together was confirmed with grazing incidence x-ray diffraction. From reflection data taken using unpolarized neutrons, the atomic density profile of the grain boundar y was determined to be (85+/-5)% of the bulk density when averaged ove r twice the grain-boundary width of (8+/-1) nm. Using this information in conjunction with the reflectivity data taken from the nickel sampl e with polarized neutrons reflection, the magnetic moment of a nickel atom was found to be between 18% and 52% larger in the twist grain bou ndary than in the bulk. The enhancement of the magnetic moment at the grain boundary is believed to result from the reduced atomic density o f the interface region. Owing to this reduction in density, the magnet ization density of the nickel interface is only somewhat enhanced, abo ut 10%, compared to that of bulk nickel.