The influence of M=Mo, Nb in Fe80(B,M,Cu)20-type alloys on the crystallization behaviour and on the magnetic properties

In amorphous Fe80(B,Mo,Cu)20-type alloys the crystallization behaviour and the magnetic properties, Curie temperature TC, coercivity HC, saturation polarization JS, and magnetostriction λS in the as-quenched state and annealed in vacuum for 1 h were investigated in dependence on the Mo content (5–7–9 at.%) with and without 1 at.% Cu and at a constant B content of 12 at.%. With increasing Mo content, TX1 and TX2 are increasing. Addition of 1 at.% Cu decreases TX1 and increases TX2. After optimal annealing of the alloys with 7 and 9 at.% Mo and 1 at.% Cu low coercivity HC≈20 A/m is established. Nearly one magnitude smaller HC values are observed at the alloy Fe80B12Mo3Nb4Cu1, HC=3 A/m. Decreasing magnetostriction λS and nanocrystal grain size with increasing Mo content are lowering the coercivity. The partial substitution of Mo by Nb reduces significantly the grain size and consequently HC. The decreasing Curie temperature with increasing Mo content of the alloys in the as-quenched state affects their magnetic properties.