• Journal of Magnetics
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• v.9 no.4
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• pp.105-108
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• 2004

The attempt for the addition of double-phase nanocomposite $Nd_2Fe_{14}BFe_3B$ powders, respectively, into several $RE_2Fe_{14}B$(RE=Pr, Nd) powders with high magnetic properties was carried out. The powders were compounded and compressed to take shape bonded magnets. By means of investigating the variation of compound magnet $B_r$, the interaction between magnetic powders was revealed. The result shows that not chemical just but physical interaction exists between elements. The compound effect of $Nd_2Fe_{14}BFe_3B$-ferrite bonded magnets was detailed studied. The functional relation was revealed between magnetic properties and ferrite content. That is $Y = 5.42 x^2 -11.34x + 6.62$. The variation of $_iH_c$ temperature coefficient ${\beta}_{iHc}$ with ferrite content was investigated. Following the ferrite content increased, ${\beta}_{iHc}$ and $h_{irr}$ were obviously decreased, compression-resistant strength was enhanced.

• Journal of Powder Materials
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• v.9 no.6
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• pp.381-393
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• 2002

Recent developments in nanocrystalline and nanocomposite rare earth-transition metal magnets are reviewed and emphasis is placed on research work at IFW Dresden. Principal synthesis methods include high energy ball milling, melt spinning, mold casting and hydrogen assisted methods such as reactive milling and hydrogenation-disproportionation-desorption-recombination. These techniques are applied to NdFeB-, PrFeB- and SmCo-type systems with the aim to produce high remanence magnets with high coercivity. Concepts of maximizing the energy density in nanostructured magnets by either inducing a texture via anisotropic HDDR or hot deformation or enhancing the remanence via magnetic exchange coupling are evaluated. With respect to high temperature applications melt spun $Sm(Co_{0.74}Fe_{0.1}Cu_{0.12}Zr_{0.04})_{7.5}$ ribbons were prepared, which showed coercivities of up to 0.53 T at 50$0^{\circ}C$. Partially amorphous $Nd_{60}Fe_xCo_{30-x}Al_{10}(0{\leq}x{\leq}30)$ alloys were prepared by copper mold casting. The effect of transition metal content on the glass-forming ability and the magnetic properties was investigated. The $Nd_{60}Co_{30}Al_{10}$ alloy exhibits an amorphous structure shown by the corresponding diffraction pattern. A small substitution of Co by 2.5 at.% Fe results In the formation of Fe-rich crystallites embedded in the Nd-rich amorphous matrix. The Fe-rich crystallites show hard magnetic behaviour at room temperature with a coercivity value of about 0.4 T, relatively low saturation magnetization and a Curie temperature of 500 K.

• Journal of Magnetics
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• v.18 no.3
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• pp.240-244
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• 2013

The influences of Gallium doping on the magnetic microstructures and corrosion behaviors of Nd-Fe-B-Ti-C alloys are investigated. The cooling rate for obtaining fully amorphous structure is raised, and the glassforming ability is improved by the Ga addition. The High Resolution Transmission Electron Microscopy image shows that the ${\alpha}$-Fe and $Fe_3B$ soft magnetic phases become granular surrounded by the $Nd_2Fe_{14}B$ hard magnetic phase. The rms and $({\Delta}{\varphi})_{rms}$ value of Nd-Fe-B-Ti-C nanocomposite alloy thick ribbons in the typical topographic and magnetic force images detected by Magnetic Force Microscopy(MFM) decreases with 0.5 at% Ga addition. The corrosion resistances of $Nd_9Fe_{73}B_{12.6}C_{1.4}Ti_{4-x}Ga_x$ (x = 0, 0.5, 1) alloys are enhanced by the Ga addition. It can be attributed to the formation of more amorphous phases in the Ga doped samples.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.45-50
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• 2015

The goal of this research is the create novel magnets with no rare-earth contents, with larger energy product by comparison with currently used ferrites. For this purpose we developed nano-sized hard-type/soft-type composite ferrite in which high remanent magnetization (Mr) and high coercivity (Hc). Nano-sized Ba-ferrite, Ni-Zn ferrite and $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ composite ferrites were prepared by sol-gel combustion method by use of glicine-nitrate and citric acid. Nanocomposite ferrites were calcined at temperature range $700-900^{\circ}C$ for 1h. According to the X-ray diffraction patterns and FT-IR spectra, single phase of NiZn-ferrite and Ba-ferrite were detected and hard/soft nanocomposite ferrite was indicated to the coexistence of the magnetoplumbite-structural $BaFe_{12}O_{19}$ and spinel-structural $Ni_{0.5}Zn_{0.5}Fe_2O_4$ that agreed with the standard JCPDS 10-0325 data. The particle size of nanocomposite turn out to be less than 120 nm. The nanocomposite ferrite shows a single-phase magnetization behavior, implying that the hard magnetic phase and soft magnetic phase were well exchange-coupled. The specific saturation magnetization ($M_s$) of the nanocomposite ferrite is located between hard ($BaFe_{12}O_{19}$) and soft ferrite($Ni_{0.5}Zn_{0.5}Fe_2O_4$). The remanence (Mr) of nanocomposite ferrite is much higher than that of the individual $BaFe_{12}O_{19}$ and $Ni_{0.5}Zn_{0.5}Fe_2O_4$ ferrite, and $(BH)_{max}$ is increased slightly.