  The Shell-ferromagnetic effect originates from the segregation process in
off-stochiometric Ni-Mn-based Heusler. In this work, we investigate the
precipitation process of L2$_1$-ordered Ni$_2$MnSn and L1$_0$-ordered NiMn in
off-stochiometric Ni$_{50}$Mn$_{45}$Sn$_{5}$ during temper annealing, by X-ray
diffraction (XRD) and $^{119}$Sn M\"ossbauer spectroscopy. While XRD probes
long-range ordering of the lattice structure, M\"ossbauer spectroscopy probes
nearest-neighbour interactions, reflected in the induced Sn magnetic moment. As
shown in this work, the induced magnetic Sn moment can be used as a detector
for microscopic structural changes and is, therefore, a powerful tool for
investigating the formation of nano-precipitates. Similar research can be
performed in the future, for example, on different pinning type magnets like
Sm-Co or Nd-Fe-B.
