Novel Ni–Mn–Co ferrite for gigahertz chip devices

Abstract

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 (ε), 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/ε ratio of Ni0.93Mn0.05Co0.02Fe2O4 was found to be 1.63 (μ/ε=7.41/4.56).