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采用磁控溅射法在硅基片上制备了Co原子分数为13.0%的Co-C纳米复合薄膜.在真空条件下,对薄膜进行退火处理,退火温度从473K逐步提高至773K,保温时间30min.形貌观察表明,未经退火处理的薄膜中,Co颗粒均匀分布在非晶C基体中,Co颗粒尺寸为1.5-3.0nm;673K退火后,Co颗粒尺寸增大.磁性能测试表明,未经退火处理的薄膜磁性较弱,随着退火温度升高,薄膜的磁化强度和矫顽力均明显增大;当退火温度增加至673—773K时,薄膜呈现出低温铁磁性、室温超顺磁性的典型颗粒体系磁性特征.磁输运特性研究表明,未经退火处理的薄膜在温度为4.2K,磁场为3980kA/m时表现出1.33%的负磁电阻,随着退火温度升高,样品磁电阻值下降;电阻与温度关系在4.2—60K范围内符合lnR-T~(-1/4)线性关系,磁输运遵循变程跳跃(variable range hopping)传导机制.
The Co-C nanocomposite films with Co atomic fraction of 13.0% were prepared on silicon substrates by magnetron sputtering.The annealed films were annealed at 473K and annealed at 773K for 30min under vacuum condition. The morphological observation shows that the Co particles are uniformly distributed in the amorphous C matrix without annealing, the size of Co particles is 1.5-3.0 nm, and the size of Co particles increases after the annealing at 673 K. The magnetic properties show that without Co The annealed films have weak magnetic properties. With the increase of annealing temperature, the magnetization and coercive force of the films increase obviously. When the annealing temperature increases to 673-773K, the films exhibit low temperature ferromagnetism and superparamagnetism at room temperature Magnetic properties of the typical particle system Magnetic transport properties of the film show that the film without annealing at a temperature of 4.2K, a magnetic field of 3980kA / m showed a negative magnetoresistance of 1.33%, with the annealing temperature increases, the sample magnetoresistance The value of resistance decreases with the increase of temperature. The linear relationship between resistance and temperature is in accordance with lnR-T ~ (-1/4) in the range of 4.2-60K. The magnetic transport follows the variable range hopping conduction mechanism.