Bulk ferromagnetic glasses in the Fe–Ni–P–B System

Abstract

The ferromagnetic metallic glass Fe 40Ni 40P 14B 6, available only as 30–50 μm thick ribbons, has been extensively studied over the last three decades. We used a flux-melting and water-quenching technique to prepare bulk glassy Fe 40Ni 40P 14B 6 alloys in the form of 2-mm diameter spheres and 1-mm diameter rods. The Curie temperature for the bulk glasses is higher than the average value of Curie temperatures reported for the rapidly quenched ribbons. The glass-transition temperature and the crystallization temperature of the bulk glasses are lower and higher, respectively, than the average values reported for rapidly quenched ribbons, making the supercooled-liquid region as wide as 42 K. The bulk glasses crystallize by a homogeneous nucleation followed by a growth at a constant rate. The nucleation rate in the bulk glasses is four orders of magnitude lower than in the rapidly quenched ribbons, suggesting that the previous thickness limitation was due to impurities in the melt (heterogeneous nucleation).