Evidence for the formation of nanoprecipitates with magnetically disordered regions in bulk math mrow msub miNi/mi mn50/mn /msub msub miMn/mi mn45/mn /msub msub miIn/mi mn5/mn /msub /mrow /math Heusler alloys/title

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Shell ferromagnetism is a new functional property of certain Heusler alloys which was recently observed in ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{45}{\mathrm{In}}_{5}$. We report the results of a comparative study of the magnetic microstructure of bulk ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{45}{\mathrm{In}}_{5}$ Heusler alloys using magnetometry, synchrotron x-ray diffraction, and magnetic small-angle neutron scattering (SANS). By combining unpolarized and spin-polarized SANS (so-called POLARIS) we demonstrate that a number of important conclusions regarding the mesoscopic spin structure can be made. In particular, the analysis of the magnetic neutron data suggests that nanoprecipitates with an effective ferromagnetic component form in an antiferromagnetic matrix on field annealing at $700\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. These particles represent sources of perturbation, which seem to give rise to magnetically disordered regions in the vicinity of the particle-matrix interface. Analysis of the spin-flip SANS cross section via the computation of the correlation function yields a value of $\ensuremath{\sim}55$ nm for the particle size and $\ensuremath{\sim}20$ nm for the size of the spin-canted region.