Superparamagnetic behaviour in melt-spun Ni₂FeAl ribbons

Heusler alloy Ni₂FeAl has been synthesized by the melt-spinning technique. The dc magnetization and frequency-dependent ac susceptibility measurements reveal that this alloy exhibits the characteristic feature of superparamagnetism. This behaviour may be associated with a structural disorder stemming from the fast quenching after the heat treatment. The small frequency-dependent ac susceptibility shifts in the blocking temperature and the existence of a pronounced peak in FC magnetization as well as Vogel-Fulcher activation processes indicate that intergranular interactions dominate in the melt-spun ribbons of Ni₂FeAl.