Evidence for the formation of nanoprecipitates with magnetically disordered regions in bulk Ni50Mn45In5 Heusler alloys

Abstract

Shell ferromagnetism is a new functional property of certain Heusler alloys which was recently observed in Ni50Mn45In5. We report the results of a comparative study of the magnetic microstructure of bulk Ni50Mn45In5 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 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 similar to 55 nm for the particle size and similar to 20 nm for the size of the spin-canted region.