The length of nanoparticles was 150 nm and the aspect ratio was 8. Metal powders were obtained by reduction of goethite nanoparticles, with the saturation magnetization and coercively of 151 emu/g and 790 Oe, respectively.

• 用NaOH制备出针状钠米粒子；长轴为150 urn；轴比约8*；进一步还原得到的金属磁记录粉的比饱和磁化强度为151 elnu/；矫顽力为790 Oe.