Unusual magnetic anisotropy in the ferromagnetic shape-memory alloy Ni50Fe23Ga27.

Unusual magnetic anisotropy of the ferromagnetic shape-memory alloy Ni50Fe23Ga27 has been observed. The anisotropy of the austenite becomes very large, even larger than that of the martensite in ribbon samples. Lowering the temperature from 300 K to 80 K, the saturation field of the austenite is dramatically increased from 200 Oe up to 6 kOe. This high-anisotropy behavior clearly highlights the demagnetization effect of the martensitic transformation. The physical mechanism is attributed to a collective effect coming from the atomic disorder, the premartensitic transformation, and the off-stoichiometric Ga-rich composition of the alloys. [ABSTRACT FROM AUTHOR]