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 Ni 50.6 Mn 36.3 Sn 13.1 as-solidified ribbons. Their elemental chemical composition, highly oriented columnar-like microstructure and single-phase character (L2 1 -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. [ABSTRACT FROM AUTHOR]