Structural and magnetic properties probed using neutron diffraction technique in Ni50−xCoxMn38Sb12 (x=0 and 5) Heusler system

• In NiCoMnSb system 2a and 2f Mn site moments increase considerably after Co doping.
• The thermal hysteresis is observed in magnetization along with the cell volume.
• ND results are in good agreement with the bulk magnetization data.
• Both the structural transition and the magnetic contribution play crucial roles.

Magnetization and neutron diffraction studies have been carried out in Ni50−xCoxMn38Sb12 (x=0 and 5) to investigate the effect of Co on the structural and magnetic properties. A comparison of the neutron diffraction data of Ni45Co5Mn38Sb12 and Ni50Mn38Sb12 alloys shows that Co substitution leads to an increase in the Mn moments. Considerably large magnetization difference associate with martensitic transition has also been observed on Co substitution. The analysis of the neutron diffraction data has revealed that the martensitic transition is accompanied by about 70% decrease in the moment and about 0.3% decrease in the cell volume. Enhanced magneto-structural coupling resulting from the Co doping has been evidenced by the magnetization as well as the neutron data. The variations in the individual site moments on Co substitution and their temperature dependencies account for the observed bulk magnetization data.