The magnetization density profile of a grain boundary in nickel (invited)
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abstract
We report the measured atomic and magnetization densities of a nickel twist grain boundary averaged over its lateral dimensions as a function of distance from the interface plane. The presence of a reconstructed 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 boundary was determined to be (855)% of the bulk density when averaged over twice the grain-boundary width of (81) nm. Using this information in conjunction with the reflectivity data taken from the nickel sample with polarized neutrons reflection, the magnetic moment of a nickel atom was found to be between 18% and 52% larger in the twist grain boundary than in the bulk. The enhancement of the magnetic moment at the grain boundary is believed to result from the reduced atomic density of the interface region. Owing to this reduction in density, the magnetization density of the nickel interface is only somewhat enhanced, about 10%, compared to that of bulk nickel.
