The effect of low temperature thermal annealing on the magnetic properties of Heusler Ni-Mn-Sn melt-spun ribbons

We report the effect of low temperature vacuum annealing (823 K; 550 °C) on the elemental chemical composition, structural phase transition temperatures, phase structure, and magnetic properties of Ni50.6Mn36.3Sn13.1 as-solidified ribbons. Their elemental chemical composition, highly oriented columnar-like microstructure and single-phase character (L21-type crystal structure for austenite) remain unchanged after this low temperature annealing. Annealed ribbons show a reduction of interatomic distances which lead to a small change in the characteristic phase transition temperatures (~3-6 K) but to a significant rise of ~73 and 63% in the saturation magnetization of the martensite and austenite phases, respectively, that can be strictly ascribed to the strengthening of ferromagnetic interactions due to the change in interatomic distances.