Site occupancy and magnetic moment of Fe in Ni2Mn0.3Fe0.7Ga alloy by neutron powder diffraction study

• Neutron powder diffraction measurements were carried out for Ni2Mn0.3Fe0.7Ga shape memory alloy system.
• It was clarified that the Mn and Fe atoms randomly occupied at 4a site in the L21-type structure.
• Magnetic moment of Fe was estimated to be about 3.0 μB, being significantly larger than that in pure bcc-Fe.

Neutron powder diffraction measurements were carried out in a wide temperature range from 14 to 500 K for Ni2Mn0.3Fe0.7Ga alloy, which undergoes a martensitic transformation from L21-type austenite phase to four layered orthorhombic-type martensite phase at about 160 K during cooling. For the diffraction pattern measured at 500 K in the paramagnetic austenite phase, it was clarified that the Mn and Fe atoms randomly occupied 4a site in the L21-type structure. Magnetic moments of Ni, Mn and Fe in the ferromagnetic austenite phase at 200 K were decided to be 0.3 and 3.3 and 3.0 μB, respectively. The magnetic moment of Fe is significantly larger than that in pure bcc-Fe of 2.2 μB. Magnetic moments of Fe in two sites at 14 K in the martensite phase were obtained to be 2.3 and 2.6 μB, respectively, suggesting that the comparatively large magnetic moments of Fe were kept even in the martensite phase. Total magnetic moment of the martensite phase at 14 K from the neutron powder diffractive analyses is 3.7 μB/f.u., being in good agreement with the result of the magnetic measurement of 3.5 μB/f.u. at 4.2 K.