Magnetic properties of full Heusler alloys Ni2MnGa1-xZx with Z = Sn or Zn.

The full Heusler alloys Ni₂MnGa_1-xZ_x were prepared by rf-induction melting, with Z = Sn over the range from x = 0 to x = 1, and with Z = Zn for x=0.0 to x=0.1. Bulk magnetic properties were measured from 77K to 450 K. The substitution of Ga with Sn is shown to strongly suppress the martensitic transition. Martensite transition temperatures decrease 25K per percent Sn. Four Sn bearing samples with x<0.05 map this effect. The ferromagnetic Curie temperature varies little with Sn content. Thirteen samples spanning the range from x=0.0 to x=1.0 show that Tc varies only from 378K (x=0) to 333K (x=1). Conversely, the substitution of Ga with Zn rapidly increases the martensitic transition temperature. With several percent Zn, the martensite transition is at room temperature. The sample preparation difficulties of Zn substitution, due to the low vaporization temperature of metallic zinc, are discussed. [ABSTRACT FROM AUTHOR]