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The influence of microstructure on magnetic properties of Sm(Co,Cu,Fe,Zr)z magnets is investigated by micromagnetic finite_element method. The demagnetization curves at different temperatures are also simulated. The calculated results show that the saturation polarization Js depends on the relative proportions of 2∶17 phase and 1∶5 phase. The coercivity and the maximum energy product increase with increasing 2∶17type cell size, while they decrease wi th increasing width of 1∶5type cell boundary. The coercivity analysis shows t hat the magnetization reversa l in Sm(Co,Cu,Fe,Zr)z magnets is mainly controlled by nucleation at cell bounda ry. The abnormal temperature dependence of coercivity is due to the fact that the cell boundary becomes less magnetic even nonmagnetic and the nucleation is difficult with increasing temperature.

Cobalt-doped ferroferriborate ((Fe1-xCox)3BO5) nanorods (NRs) have been synthesized by using a high-temperature organic-solution-phase method, and characterized by high resolution transmission electron microscope (HRTEM) and SQUID. The aspect ratios of the NRs are tuned by reductive decomposition of Fe(acac)3 and Co(acac)2 with a predetermined ratio. HRTEM showS that the sample is polycrystalline NRs and the top view of a NR tip reveals a multiply-twined structure. Magnetization curves indicate that (Fe1-xCox)3BO5 NRs are ferromagnetic above room temperature and the antiferromagnetic component is included, the magnetic properties are dramatically modified by Co substitutional doping. The NRs are expected to be used to study the mechanical properties of biological macromolecules.