Hysteresis and relaxation of hard-soft nanocomposite samples

We present experimental results on the hysteresis and relaxation of Fe/Ba hexaferrite composite samples prepared by ball milling starting from precursor Fe and Ba hexaferrite particles. Our results show that, for maximum applied fields of up to 8 kOe, the measured loops show a shift of up to 85 Oe. The compositional dependence of that loop displacement presents two maxima (at approximately x=0.3 and x=0.7) and a minimum at x=0.5. These results are discussed in terms of the dipolar coupling between both phases. (C) 2000 American Institute of Physics. [S0021- 8979(00)63708-8].