Effects of Cu substitution for Nb on magnetic properties of Fe-based bulk metallic glasses

•Saturation magnetization Ms increases monotonically with Cu substitution.•Better effective permeability and coercive force present with minor Cu substitution•No decrease in glass-forming ability with better magnetic properties

The effects of minor Cu substitution for Nb in Fe72B20Si4Nb4-xCux (x = 0.0, 0.1, 0.2, and 0.3) bulk metallic glasses (BMGs) on the magnetic properties were investigated. With increasing Cu content from x = 0 to 0.3, the critical diameters are kept constant at 1.5 mm for all Fe-based BMGs rods. Meanwhile, the increasing saturation magnetization from 1.19 to 1.27 T, and the decreasing coercive force from 2.5 to 1.5 A/m were found, with the effective permeability improved from 20,000 to 24,500. This work reveals the connection between the enhanced magnetic properties and Cu substitution. It may shed light on the design of Fe-based BMGs with better magnetic properties and larger glass-forming ability concurrently.