Microwave Magnetic Properties Of 2:17 Rare Earth-3d Transitionmetal Intermetallic Compounds Powders/resin Epoxy Compolites With Planar Magnetic Anisotropy

The rare earth-3d transitionmetal intermetallic compounds with planar magnetocrystalline anisotropy can overcome the limitation of the Snoek's limit. The value of (μi-1)fr can be highly improved and the permeability and resonance frequency can also both be increased at the same time.The intermetallic compounds Nd2(Co1-xFex)17 (0≤x≤1) and Ce2(CoxFe1-x)17(0≤x≤0.8) microparticles were prepared by arc melting and followed ball milling. The crystal structure, static magnetic properties and magnetocrystalline anisotropy of the intermetallic compounds microparticles were studied. The resin epoxy composites of the intermetallic compounds microparticles with 35 vol % powders were prepared, and the microwave magnetic properties were studied. The main results are shown as follows:(1) Nd2(Co1-xFex)17(0≤x≤1) possess planar magnetocrystalline anisotropy.The largest value of permeability is 2.81 when x=10 in the whole x range of 0-1,and the value of the imaginary part of complex permeability is 1.00 at the resonance frequency of 8.9 GHz.(2) Ce2(Co1-xFex)17 possess uniaxial magnetocrystalline anisotropy with x=0, 0.1,0.2,0.3 and 0.4; Ce2(Co0.5Fe0.5)17 possess conical planar magnetocrystalline anisotropy; Ce2(Co1-xFex)17 possess planar magnetocrystalline anisotropy with x=0.6, 0.7 and 0.8. The values of (μi-1)fr of the resin epoxy composites of Ce2(Co1-xFex)17 with planar magnetocrystalline anisotropy (x=0.6,0.7 and 0.8) are much higher than that of the resin epoxy composites of Ce2(Co1-xFex)17 with uniaxial magnetocrystalline anisotropy (x=0,0.1,0.2,0.3 and 0.4). The value of (μi-1)fr of the resin epoxy composites of Ce2(Co0.5Fe0.5)17 is between the two kinds composites. The resin epoxy composites of Ce2(Co1-xFex)17 with planar magnetocrystalline anisotropy can overcome the limitation of the Snoek limit. In the whole x range of 0-0.8, the largest value of permeability can be obtained to be 4.27 when x=0.8, and the value of the imaginary part of complex permeability is 1.67 at the resonance frequency of 5.2 GHz.(3) Multiwalled carbon nanotubes filled with face centered cubic (fcc) Co nanoparticles (MWCNTs/Co) were successfully prepared by a chemical reducing method. The relative permeability and permittivity spectra of MWCNTs/Co resin composites with 50 wt % powders were measured in the frequency range of 0.1-18 GHz. Three resonance absorption peaks are observed in theμ"-f spectrum: the peak around 5.0 GHz can be attributed to natural resonance, while the other two appear around 10.6 GHz and 16.9 GHz are induced by exchange resonance. It is found that the peak with minimum reflection loss (RL) value moves to lower frequencies and the RL value increases from 4.2 to 10.1 dB with the increase of the absorber's thickness from 2mm to 6mm.