Structural, thermal, and magnetic properties of Fe79Mo B20−Cu1 magnetic amorphous and nanocrystalline alloys

Abstract Fe79MoxB20−xCu1 amorphous and nanocrystalline alloys (x = 2, 4, 6, 8 and 10) were studied to investigate the influence of Mo and B contents on crystallization, structural, and magnetic properties. Samples were prepared by rapid solidification of alloy ingots using a single wheel melt spinner. Primary and secondary crystallization temperatures increased with the Mo content in the alloys. A wide primary phase stability range (~280 °C) is achieved for the Fe79Mo10B10Cu1 alloy. The alloys with x = 8 and 10 exhibited a fine-grained microstructure (~5 nm) of BCC Fe phase after isothermal annealing at the primary crystallization temperature. Magnetization at an applied field of 1.19 × 106 A/m (15 kOe) of the annealed alloys decreases with the Mo content, and coercivity of less than 100 A/m is attained at x = 8 and 10. Grain size increased to ~25 nm for x = 2 and 4 under the same thermal treatment, which resulted in higher coercivities. The Curie temperature of the amorphous alloys was observed to decrease with increasing Mo content, lowering below room temperature at x = 10. A good thermal stability of nanoscale microstructure is characterized for the x = 10 alloy at elevated temperatures (650 °C and 700 °C).