Fabrication of Full‐Density Mg ‐Ferrite/ Fe – Ni Permalloy Nanocomposites with a High‐Saturation Magnetization Density of 1 T

Dense nanocomposites consisting of spinel Mn ‐doped Mg ‐ferrite and permalloy, ( Mg [ Fe _{1 − x} Mn _x ] ₂ O ₄ (0 ≤ x ≤ 0.4)/53 Fe –47 Ni ), have been fabricated from powder mixtures of MgO /α‐ Fe ₂ O ₃ / MnO and N ₂ ‐atomized metal particles utilizing high‐pressure cold isostatic press ( CIP ), pulsed electric current pressure sintering ( PECPS ), and capsule‐free hot isostatic pressing ( HIP ). Metal particles were coated with the mixed oxide powders homogeneously under high shear compression in Ar. The coated powders were densified into relative densities of 83–85% by high pressure CIP ing (1 GP a). They were then presintered at 823 K for 3 min under uniaxial pressure of 100 MP a in Ar using a PECPS . The pre‐sintered bodies had relative densities of 93–95% composed of spinel ferrite and permalloy; the mixed metal oxides were changed into magnesium ferrites by heating briefly at low temperature. Then, HIP (1123 K/6 h/196 MP a‐Ar) was adopted to densify the pre‐sintered bodies into a nearly full density; furthermore, a sintering atmosphere control was performed using ferrite muffles to maintain both phases. Sintered materials consisting of granular metal particles (φ 8.5 μm) isolated and surrounded by a thin ferrite discontinuous layer (0.2–1.3 μm) with a relative density ≥99.5% revealed both a saturation magnetization density ≥1 T and moderate permeability values of 30–35 at 1 MH z.