High B s Fe84−xSi4B8P4Cux (x = 0 – 1.5) nanocrystalline alloys with excellent magnetic softness

The magnetic properties of annealed Fe84−xSi4B8P4Cux (x = 0, 0.5, 0.75, 1.0, 1.25, 1.5) soft-magnetic alloys prepared by melt–spinning were investigated. In this alloy system, the appropriate addition of the Cu element promotes the precipitation of α-Fe(Si), as well as inhibits the precipitation of other phases. The saturation magnetic flux density Bs increases and the coercivity Hc markedly decreases simultaneously with increasing Cu content until x = 1.25. The Fe82.75Si4B8P4Cu1.25 alloy annealed at 873 K for 1.8 ks shows a high Bs of 1.83 T and excellent soft-magnetic properties such as a low Hc of 2.1 A/m and a high effect permeability of 31 600. It is found that a 1%–1.25% addition of Cu is effective for the improvement of soft-magnetic properties for the present alloy system.