强磁靶共溅射法制备具有室温磁电阻特性的Co-TiO2纳米复合薄膜

Co-TiO₂纳米复合薄膜作为一种新型自旋电子材料, 由于具有良好的生物相容性, 近年来受到广泛关注。但在制备过程中, 磁性金属Co处于氧化气氛, 容易部分氧化, 从而影响薄膜的隧道磁电阻性能。为了抑制磁性金属的氧化, 提高金属态含量, 本研究通过强磁靶共溅射法制备了Co-TiO₂纳米复合薄膜。该方法采用的强磁靶头, 磁场强度高、分布均匀, 可以提高溅射粒子的能量和溅射速率, 降低因高能粒子碰撞而发生氧化的概率。因此强磁靶共溅射法能明显抑制金属Co的氧化, 提高纳米复合薄膜的自旋极化率。所制备的Co-TiO₂纳米复合薄膜主要由非晶态的TiO₂基体和分散其中的Co颗粒组成。通过调节金属Co颗粒尺寸和分布状态, 在电学上实现了金属态向绝缘态转变, 在磁学上实现了铁磁性向超顺磁性转变。Co含量为51.3at%时, Co-TiO₂纳米复合薄膜表现为高金属态和高电阻率, 并且实现了高达8.25%的室温隧道磁电阻。强磁靶共溅射法使Co-TiO₂纳米复合薄膜的室温磁电阻性能得到了进一步提高, 这对于磁性金属—氧化物纳米复合薄膜的研究有着重要的意义。

Room Temperature Magnetoresistance Property of Co-TiO2 Nanocomposite Film Prepared by Strong Magnetic Target Co-sputtering

Co-TiO₂ nanocomposite film is a novel spin electron material with good biocompatibility, attracting wordwide attention in recent years. However, during the preparation process, the magnetic metal is exposed to the oxidizing atmosphere, which tends to form partial oxidation, thus affecting the properties of the tunnel magnetoresistance. In order to inhibit the oxidation of magnetic metal and improve the metal state, Co-TiO₂ nanocomposite films were prepared by strong magnetic target co-sputtering. In this method, the strong magnetic target head has the characteristics of high magnetic field intensity and uniform distribution, which can significantly improve the sputtering particle energy and sputtering rate. This process could reduce the probability of oxidation caused by high energy particle collision during sputtering. Therefore, the method can inhibit the oxidation of metal Co, improve the spin polarizability of nanocomposite films. The Co-TiO₂ nanocomposite film is mainly composed of amorphous TiO₂ matrix and dispersed Co particles. By adjusting the particle size and distribution of Co particles, the electrical properties of the films show the transition from metal state to insulated state. Moreover, the magnetic properties of the films show the transition from ferromagnetic state to superparamagnetic state. When the Co content is 51.3at%, the Co-TiO₂ nanocomposite films exhibit high metal state and high resistivity, and room temperature tunneling magnetoresistance up to 8.25%. By strong magnetic target co-sputtering, the room temperature magnetoresistance performance is improved in Co-TiO₂ nanocomposite films, which is valuable for the study of magnetic metal-oxide nanocomposite films.