Magnetization processes in hybrid magnets

Injection-molded, oriented hybrid magnets consisting of mixtures of BaO⋅6Fe2O3 and MQP-Q (exchange-coupled Nd2Fe14B+α-Fe) are compared to bonded magnets made only from ferrite or MQP-Q. The magnetic fractions of the hybrid magnets consist of 80, 60, or 40 wt % ferrite blended with 20, 40, or 60 wt % MQP-Q. The microstructure was investigated by x-ray diffraction, scanning electron microscopy, atomic force microscopy, and magnetic force microscopy. Atomic and magnetic force microscopy images indicated differences between the physical and magnetic microstructures. Magnetic interactions were studied via isothermal remanence (IRM) and dc-demagnetization (DCD) remanence curves and Henkel plots. In contrast to what is observed in exchange spring magnets, the IRM and DCD susceptibilities of all magnets present peaks of nearly the same width, centered at roughly the same value of the magnetic field, consistent with weak dipolar interactions between magnetic particles. The IRM susceptibilities show structure associated with magnetic inhomogenieties in the samples.