Magnetization processes in hybrid magnets

Injection-molded, oriented hybrid magnets consisting of mixtures of BaO . 6 Fe(2)O(3) and MQP-Q (exchange-coupled Nd2Fe14B+alpha-Fe) are compared to bo nded 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 differenc es between the physical and magnetic microstructures. Magnetic interactions were studied via isothermal remanence (IRM) and de-demagnetization (DCD) r emanence curves and Henkel plots. In contrast to what is observed in exchan ge 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 m agnetic field, consistent with weak dipolar interactions between magnetic p articles. The IRM susceptibilities show structure associated with magnetic inhomogenieties in the samples. (C) 1998 American Institute of Physics. [S0 021-8979(98)17211-0].