Influence of Magnetic Field Annealing on Soft Magnetic Properties for Nanocrystalline Fe39.4–xCo40Nb2.6Si9B9Cux Alloys

The influence of magnetic field annealing and Cu content on saturation magnetostriction
$\lambda _{s}$
, effective magnetic anisotropy
$< {\textit {K}} >$
, and temperature dependence of initial permeability (
$\mu _{i}$
–
$T$
curves) for nanocrystalline Fe
_39.4−x
Co
₄₀
Nb
_2.6
Si
₉
B
₉
Cu
_x
(
$x=0.5$
, 1, 1.5) alloys was investigated. The
$\lambda _{s}$
and <
K
> of the alloys were both decreased with Cu content increasing. Magnetic field annealing can obviously reduce
$\lambda _{s}$
, which is due to the rearrangement of random oriented magnetic domain along applied field direction. The increase of <
K
> is due to the presence of a coherent induced magnetic anisotropy
K
$_{u}$
under magnetic field annealing, which can be explained in terms of the directional atomic pair ordering theory. In addition, the inverse dependence between
$\mu _{i}$
and <
K
> could be changed in the case of magnetic field annealing. In contrast to nonmagnetic field annealing, magnetic field annealing can enhance the room- and high-temperature initial permeability of nanocrystalline Fe
_39.4−x
Co
₄₀
Nb
_2.6
Si
₉
B
₉
Cu
_x
(
$x=0.5$
, 1, 1.5) alloys; the reason of which was also analyzed.