Improved soft magnetic properties of nanocrystalline Fe-M-B-Cu (M = Zr, Nb) alloys with high saturation magnetic flux density and zero-magnetostriction

The compositional dependence and the annealing temperature dependence of the soft magnetic properties for the nanocrystalline Fe-M-B-Cu (M = Nb, Zr) alloys have been investigated. The high effective permeability, μ_e, above 100,000 at 1 kHz combined with the high saturation magnetic flux density, B_s, of 1.45 to 1.61 T have been obtained in the Fe_100-a-b-c-dNb_aZr_bB_cCu_d (3.25 ≤ a ≤ 3.5, b ≈ a, 6.5 ≤ c ≤ 8 and 1 ≤ d ≤ 2) alloys. These alloys consist of fine bcc grains with less than 10 nm in size and exhibit nearly or exactly zero-magnetostriction. This excellent μ_e value is comparable to those of nanocrystalline Fe_73.5Si_13.5B₉Nb₃Cu₁ alloy and zero-magnetostrictive Co based amorphous alloys, and the high B_s is comparable to those of Fe based amorphous alloys with good soft magnetic properties. The magnetostriction of the nanocrystalline Fe-M-B based alloys also can be controlled by changing the annealing (crystallizing) temperature. The nanocrystalline Fe-M-B based alloys with excellent soft magnetic properties as well as high B_s and zero-magnetostriction are expected to be used for many kind of magnetic parts and devices.