Producing Soft Magnetic Composites by Spark Plasma Sintering of Pseudo Core-Shell Ni-Fe Alloy@Mn0.5Zn0.5Fe2O4 Powders

Soft magnetic composite (SMC) cores have been obtained by Spark Plasma Sintering (SPS) using pseudo core-shell powders. Pseudo core-shell powders are formed by a core of soft magnetic particle (nanocrystalline permalloy or supermalloy) surrounded by a thin layer (shell) of nanosized soft ferrite (Mn0.5Zn0.5Fe2O4). Three compositions of pseudo core-shell powders were prepared, with 1, 2 and 3 wt.% of manganese-zinc mixt ferrite. The pseudo core-shell powders were compacted by SPS at temperatures between 500 and 700 degrees C, with a holding time ranging from 0 to 10 min. Several techniques have been used for characterization of the samples, both, powders and compacts X-ray diffraction (XRD, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), magnetic hysteresis measurements (DC and AC) and electrical resistivity. The electrical resistivity is in the order of 1 x 10(-2) omega m, 3-4 orders of magnitude higher than supermalloy electrical resistivity. The SPS at lower temperatures (500 degrees C) conserves the initial phases of the composite, but increasing the sintering temperature and/or sintering time produces a solid-state reaction between the alloy and ferrite phases, with negative consequence on the magnetic properties of the compacts. The initial relative permeability is around 40 and remains constant until to 2000 Hz. The power losses are lower than 2 W/kg until to 2000 Hz.

Automated summary

Soft magnetic composite (SMC) cores were obtained by Spark Plasma Sintering (SPS) using pseudo core-shell powders, consisting of a core of soft magnetic particle surrounded by a thin layer of nanosized soft ferrite. Different compositions of pseudo core-shell powders were prepared, and the compacts were characterized using various techniques. The electrical resistivity of the SMC cores is significantly higher than that of supermalloy, and the magnetic properties are affected by the sintering temperature and time. The initial relative permeability and power losses of the SMC cores are stable up to a certain frequency.