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 <K>, and temperature dependence of initial permeability (mu(i)-T curves) for nanocrystalline Fe39.4-xCo40Nb2.6Si9B9Cux (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 Fe39.4-xCo40Nb2.6Si9 B9Cux (x = 0.5, 1, 1.5) alloys; the reason of which was also analyzed.