包裹SiO_2薄层的Fe_3O_4纳米颗粒体系中增强的隧穿磁电阻效应

Fe3O4是一种半金属材料,在金属磁性氧化物当中有着较高的居里温度(858K),因此在自旋电子应用当中有广阔的前景。通过在直径大约200nm的单分散Fe3O4微球外包裹一层绝缘的SiO2壳层而人工引入晶界,再冷压烧结成块状制成样品。与包膜前相比,样品的磁电阻效应大为增强,而且两者磁电阻的行为明显不同,后者在高场下出现一个线性关系,这是由SiO2晶界引起的,相关的探索给出了一条新的提高磁电阻效应的途径。

Enhanced Tunneling Magnetoresistance in Fe_3O_4 Nanopowder Compact Coated with SiO_2

Fe3O4 is considered to be half metal nature and has a comparatively high Curie temperature of 858 K compared with other metal oxides, which makes it more attractive in spin-electronic application. The extrinsic magnetoresistance of Fe3O4 has been studied extensively, however, so far few progress is acheieved. Here, a new way is given to obtain higher MR. Fe3O4 nanospheres with the average diameter of about 200 nm is prepared and coated by SiO2, which forms a shell of several nms. The nanopowder with SiO2 shells, which serves as grain boundaries, is pressed and then sintered into compacts, which show enhanced MR. At different temperatures MR curves of compacts with SiO2 and without SiO2 differ much, and the former display a linear respond at high field range, which is interpreted as the existance of insulating SiO2 grain boundaries.