  The martensitic and magnetic phase transformations in MnNiGe1-xSnx (0 \leq x
\leq 0.200) alloys were investigated using X-ray diffraction (XRD),
differential thermal analysis (DTA) and magnetization measurements. Results
indicate that the increasing Sn substitution in MnNiGe1-xSnx results in (i)
decrease of martensitic transformation temperature from 460 to 100 K and (ii)
conversion of AFM spiral to antiparallel AFM strcuture in martensite. Based on
these, the remarkable magnetic-field-induced PM/spiral-AFM and FM/AFM
magnetostructural transformations and, large positive and negative
magnetocaloric effects are obtained. The magnetoresponsive effects of
MnNiGe1-xSnx alloys are enhanced by Sn substitution. A structural and magnetic
phase diagram of MnNiGe1-xSnx alloys has been proposed.
