The present work aims to address the effect of self-doping and a combined perturbation of self- and vacancy doping on the structural, magnetic, and magnetofunctional properties of MnNiGe-based magnetic equiatomic alloys of nominal compositions ${\mathrm{Mn}}_{1-x}{\mathrm{Ni}}_{1+x}\mathrm{Ge}$ (for $x$ = 0.2 and 0.15), ${\mathrm{Mn}}_{1+y}{\mathrm{Ni}}_{1-y}\mathrm{Ge}$ (for $y$ = 0.2 and 0.22), and ${\mathrm{Mn}}_{1+z}{\mathrm{Ni}}_{0.9-z}\mathrm{Ge}$ ($z$ = 0.03 and 0.06). Experimental findings reveal that all six alloys undergo martensitic type first-order phase transition and the transition is found to be shifted towards lower temperature with increasing doping concentration. Structural investigation reveals the incomplete nature of the martensitic phase transitions. A substantial magnetic entropy change near the martensitic phase transition temperature suggests the materials applicability as magnetic refrigerant. Interestingly, perturbation at the magnetically ordered transition metal site (Mn site) through self-doping shows larger impact on the structural and magnetic properties compared to the perturbation at the nonmagnetic transition metal site (Ni site). The introduction of vacancy at the Ni-site results in a larger impact on the incompleteness in the martensitic phase transition present in dual-doped alloys. Field-induced metamagnetic transition, nonmonotonicity in the inverse magnetocaloric effect behavior, and the presence of a possible spin-reorientation transition have also been noticed in the alloys with coexisting self- and vacancy doping.

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• Magnetism
• Phase transitions
• Shape memory effect
• Magnetic refrigeration
• Polycrystalline materials
• Shape-memory materials
• Transition metal alloys
• Arc discharge
• Magnetization measurements
• X-ray powder diffraction