磁场下合成Fe3O4粉体的隧道磁阻

通过在半金属Fe₃O₄合成过程中外加磁场的方法，改变样品粒子的表面结晶状态和晶格缺陷，研究了由此引起的Fe₃O₄输运性质的变化.合成的Fe₃O₄粉体的主要导电机理均为自旋极化隧穿和高阶跃迁电导，电阻随温度升高成指数降低，电阻与电压显示了非线形相关性，磁阻与磁场的关系为蝴蝶形，是典型的隧道磁阻特征.与没有外加磁场时合成的样品比较，外加磁场合成的样品显示了更低的电阻和更高的磁阻.关键词：磁阻隧穿表面晶格缺陷

Tunneling magnetoresistance of Fe3O4 compacts prepared in magnetic field

The magnetite particles were prepared in magnetic field in order to improve the surface crystallinity and reduce the lattice defests of particles. The magnetotransport properties of as-prepared magnetite compact were investigated and compared with that prepared without magnetic field. Spin polarization tunneling and high order hopping conductance were the main conduct mechanisms. The resistance decreased almost exponentially with increasing temperature, and was noncollinearity dependent on the voltage. Magnetoresistance vs magnetic field curves were butterfly-like, which was characteristic of tunneling magnetoresistance. The results showed that the sample prepared in magnetic field had lower resistance and higher magnetoresistance, maybe due to the particles having better crystallinty in the surface and less lattice defect. Magnetoresistance of both samples decreased slowly with increasing temperature.