Search

Theoretical saturation magnetization and magnetocrystalline anisotropy energy (MAE) of τ-phase (face-centered tetragonal) Mn50Al50 alloy were obtained by first principles calculations, and the alloy was fabricated to compare the experimental values with the theoretical predictions. The calculated magnetic moment and MAE for τ-phase Mn50Al50 were 2.37) μg/ f.u. and 0.259 meV/f.u. (1.525×106 J/m3), respectively, which result in the maximum energy product (BH)max of 12.64 MG Oe and the magnetocrystalline anisotropy field of 38 kOe. The saturation magnetization for τ-phase Mn54Al46 alloy was measured to be 98.3 emu/g, which gives 4.7 MG Oe of (BH)max. The magnetization is about 70% of the theoretical value of 144 emu/g. [ABSTRACT FROM AUTHOR]

The effect of Mn and/or Co doping in Ni–Mn–Co ferrite on the static, dynamic magnetic properties, and thermal magnetic stability were investigated for high frequency microwave applications up to the gigahertz range. Saturation magnetization and coercivity increased with increased substitution of Mn and Co, respectively. Both Mn and Co substituted Ni–Mn–Co ferrite exhibited higher thermal stability factor rather than Ni–Mn and Ni–Co ferrites. The highest thermal stability factor was achieved to be -12.0×10-4 °C/ppm for Ni0.93Mn0.05Co0.02Fe2O4. The second highest, -11.88×10-4 °C/ppm, was measured for Ni0.7Mn0.05Co0.02Fe2.23O4. Permeability (μ), permittivity ([variant_greek_epsilon]), and cutoff frequency of Ni0.93Mn0.05Co0.02Fe2O4 and Ni0.7Mn0.05Co0.02Fe2.23O4 showed 7.41, 4.56, 1084 MHz, and 3.87, 4.55, 1436 MHz, respectively. Furthermore, the μ/[variant_greek_epsilon] ratio of Ni0.93Mn0.05Co0.02Fe2O4 was found to be 1.63 (μ/[variant_greek_epsilon]=7.41/4.56). [ABSTRACT FROM AUTHOR]

Magnetic properties of sol-gel and conventional ceramic processed Ba3Co2Fe2O41 hexaferrite were investigated and compared for terrestrial digital multimedia broadcasting (T-DMB) antenna application. All of the synthesized powder and sintered body showed almost single Z-phase. The loss tan δ of sol-gel processed and sintered Co2Z hexaferrite was 0.010 at 200 MHz, while conventional ceramic processed and sintered Co2Z showed 0.068. The ωd (resonance frequency of domain wall) and ωs (resonance frequency of spin components) of sol-gel and ceramic processed hexaferrites were estimated to be 10 and 1160 MHz and 17 and 1025 MHz, respectively. The frequency difference between ωd and ωs (1150 MHz) for the sol-gel processed hexaferrite is wider than that (1008 MHz) for the ceramic processed hexaferrite. The permeabilities of sol-gel and ceramic processed hexaferrites were 6.91 and 9.23 at 200 MHz, respectively. Both permeabilities are higher than 6.88 and 7.64 of corresponding permittivities at the same frequency, respectively. It is found that the sol-gel processed and sintered Z-type hexaferrite meet desired low-loss tan δ and broadband for T-DMB antenna. [ABSTRACT FROM AUTHOR]