| Nonmagnetic Cr layer interface and anisotropy of SmCo/Fe system were study in this article, respectively. SmCo/Fe bilayers with different thickness of nonmagnetic mid-layer Cr layer were prepared by magnetron sputtering, We systematically study the effect of the inserted Cr layer on the SmCo/Fe bilayer. The effects of dry milling, annealing and surfactant assisted ball milling conditions on the particle morphology, size, phase structure and magnetic properties of the powders have been investigated systematically. Effects of magnetic field heat treatment on the structure and magnetic properties of Sm-Co/α-Fe nanocomposite permanent magnetic materials fabricated by high energy ball milling are also investigated. Several techniques, for example, X-ray diffraction(XRD), Inductively coupled plasma emission spectrometer(ICP), Vibrating sample magnetometer(VSM) and Superconducting quantum interface(SQUID) have been employed to study the composition, morphologies, size distribution, pahse constitution, microstructure and magnetic properties. The mechanism of nonmagnetic Cr layer effect was careful ly analyzed, and discussed the magnetic field heat treatment and surfactant aided ball mill for the microstructure and magnetic properties of SmCo/Fe magnet, especially the anisotropy. The main achievements are as follows:(1) We prepared suitable composition target by powder metallurgy and melt-casting,respectively, which can prepared high-performance single-layer SmCo film. It found that the coercivity increases as the sputtering power increases, hysteresis loop sharp was strongly influenced by the texture of Cr buffer layer, which was determined by its sputtering temperature. Since the interface roughness is larger, Cr intermediate layer thickness is smaller dispersed between the two phases. When the Fe layer thickness at the critical thickness or less, the thin intermediate Cr layer act as a pinning point in the magnetization reversal process, improving the coercivity of the system, thereby increasing the maximum energy product. When the Fe layer thickness exceeds the critical thickness, the nucleation field system with increasing Cr intermediate layer thickness decreases linearly, indicating the added Cr intermediate layer weakens the exchange coupling between the two phases.(2) After a magnetic field heat treatment below 700 oC on as-milled amorphous Sm-Co/α-Fe samples, showing a hysteresis loop of single phase characteristic, are obtained. The coercivity increases with the increase of annealing temperature. The coercivity, remanence and remanence ratio of the Sm-Co/Fe nanocomposite magnets are all enhanced after a heat treatment at a magnetic field as compared with those of nanocomposite magnets heat treated without a magnetic field. X ray diffraction analysis shows that the diffusion between the Sm-Co hard and α-Fe soft phases is suppressed by the magnetic field applied during the heat treatment process. Magnetic field heat treatment also makes the direction of c axis of Sm-Co hard grains along the heat treatment magnetic field direction, leading to an enhancement of magnetic anisotropy of the Sm-Co/Fe nanocomposite magnets.(3) the anisotropic SmCo5/Fe nanocomposite permanent magnetic nanoflakes were fabricated by surfactant assisted ball milling the powers obtained from the high energy dry milling and subsequent annealing. It was found that the SmCo+20wt.%Fe powders are completely amorphous after dry milling for 5h. The nanocomposite particles with mixture of hard Sm-Co and soft Fe nanocrystallines were obtained after annealing the dry milled powders at 500-650 oC and all samples show a hysteresis loop of single hard phase character. After further surfactant assisted ball milling the powders for 4h, the Sm-Co/Fe nanocomposite magnetic nanoflakes which exhibit also a characteristic of single hard phase hysteresis loop and an improved anisotropy were obtained. |
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