No abstract

Surfactant-assisted high energy ball milling technique is a new method of producing magnetic nanoparticles. In this study, permanent magnetic SmCo 5 nanoparticles and nanoflakes with high room-temperature coercivity values and narrow particle size distributions were produced by this technology and a subsequent size-selection process. The SmCo 5 nanoparticles with average particle sizes of 9.8 and 47.5 nm, exhibited room-temperature coercivity values of 6.8×10 4 and 7.3×10 5 A/m, respectively, while the SmCo 5 nanoflakes, with the mean particle size of about 1.4 μm and average thickness of 75 nm, showed excellent permanent magnetic properties with an obvious c-axis crystal texture, a strong magnetic anisotropy and high coercivity values of 5.5×10 5 and 1.6×10 6 A/m in their easy-axis and hard-axis directions, respectively. The coercivity values of SmCo 5 nanoparticles and nanoflakes exhibited a significant particle size dependance effect.

The Fe doped Ca1-xFexMnO3(x=00.12) powder and bulk samples are fabricated by citric acid sol-gel and ceramic preparation process, the samples are analzed by X-ray diffraction pattern and electrical constant measurement. The results show that all samples are of single phase, the lattice constants are gradually lowered by Fe doping for Ca site, and the crystalline grain growth is restrained. All the bulk samples have semiconductor transporting characteristics in the whole temperature range of measurement. The transportation mechanism is not changed. The energy for polarons to hop is increased for doped samples and thus the electrical resistivity is increased by increasing Fe doping concentration.