Structural and Magnetic Properties of Ni₁₊ MnSb Bulk Heusler Composite Materials

Variation in structural and magnetic properties with changing valence electron count (VEC) has been studied well in the family of Heusler compounds, while such changes in VEC resulting in half-Heusler (HH) and full-Heusler (FH) composites have not been reported to observe their effect on the magnetic properties. Herein, we have synthesized the composite of HH and FH phases in Ni₁₊ MnSb (x = 0.0, 0.3, and 0.6) via changing VEC from 22 to 28 in order to investigate the structural and magnetic properties. Interestingly, a transition from half-metallic ferromagnetic to normal ferromagnetic was revealed in Ni₁₊ MnSb (x = 0.0, 0.3, and 0.6) materials with increasing VEC. The structural investigations of these materials were performed using a X-ray diffraction technique and analyzed by Rietveld Refinement software for all the samples. Rietveld analysis reveals the presence of a significant amount of the NiSb paramagnetic impurity phase in the HH NiMnSb system while in the case of Ni₁₊ MnSb (x = 0.3 and 0.6), no such impurity phase was observed. Only FH and HH phases in Ni₁₊ MnSb (x = 0.3 and 0.6) samples were noticed. The magnetic measurement performed on samples employing a vibrating sample magnetometer reveals the ferromagnetic ordering in all samples. A weak hysteresis loop with saturated magnetic moments ∼2.99 and 2.98 μ_B at room temperature was observed for NiMnSb and Ni_1.3MnSb, respectively, while a strong hysteresis loop with lower magnetic moment of 0.88 μ_B was observed in the Ni_1.6MnSb composite. Furthermore, the observed magnetic moments for the composite Ni_1.3MnSb have been explained on the basis of the Slater-Pauling rule in relation to VEC.