Transport properties of shell-ferromagnetic Heusler precipitates in decomposed Ni49.8Mn45.1Sn5.1 and decomposition limit for Ni50Mn50−xSnx alloys

•Determining the limit of decomposition for Ni50Mn50−xSnx Heuslers on the basis of shell-ferromagnetism.•Magneto resistance effects in core-shell type Heusler precipitates.•Structural and magnetic meta-stabilities Ni-Mn-based Heuslers. Shell-ferromagnetism is observed in Mn-rich NiMn-based Heusler alloys as a result of phase-separation. Off-stoichiometric NiMn-based Heusler alloys decompose into a dual-phase composite when annealed under a magnetic field. As a result of this process, an initially anti-ferromagnetic Heusler alloy gains hard-ferromagnetic properties with a nearly 10 Tesla coercive field of a core/shell structured precipitate. In the present study, Ni50.1Mn42.1Sn7.8 and Ni50.4Mn36.6Sn13.0 alloys are investigated for magnetic and structural instabilities and shell-ferromagnetic decomposition to obtain information on the compositional limits of the decomposition. Furthermore, we investigate the magneto-transport properties of shell-ferromagnets obtained by annealing Ni49.8Mn45.1Sn5.1 in a magnetic-field.