To obtain a strong electromagnetic force, a soft magnetic material with a high saturation induction density and low remanence is often applied for the iron core and armature.
where [M.sub.s] is the saturation magnetization; [B.sub.r] is the residual magnetic flux density; [B.sub.s] is the saturation induction density; Hs is the magnetic field intensity corresponding the saturation induction density; [H.sub.c] is the coercivity; [[mu].sub.0] is the constant permeability of vacuum.
With the increase of H, B increases quickly at first, but its increase becomes slow and gradually approaches the saturation induction density [B.sub.s].
Every magnetic material has a different saturation induction density [B.sub.s] and maximum permeability [[mu].sub.max].
Yoshizawa and his colleagues showed on Fe-Cu-Nb-Si-B and later on Fe-Cu-M-B-Si family (where M = Nb, V, Mo, Zr) nanocrystallized alloys, exceptional magnetic characteristics: saturation induction
of 1.2 T, low coercivity, magnetic permeability at high frequencies above [10.sup.3] (Codrean et al., 2007).