FeCo-SiO_2颗粒膜的磁性和隧道磁电阻效应研究

Magnetic Properties of FeCo-SiO_2 Granular Film and Its Tunneling Magnetoresistance Effect

用射频共溅射的方法制备了不同金属含量φ的 Fe- Si O2 金属 -绝缘体颗粒膜 ,系统研究了薄膜的微结构、磁性以及隧道磁电阻 ( TMR)效应 .在φ=0 .33处得到最大磁电阻比 RTMR为- 3. 3% .在同样的制备条件下保持φ =0 . 33,用 Co 取代 Fe 得到一系列的( Fe10 0 -x Cox) 0 .33( Si O2 ) 0 .67的颗粒膜 .对其 TMR的研究发现在 x =53时得到最大的磁电阻比为 -4 .3% ,且 Co对 Fe的替代基本没有影响薄膜的微结构 .由 Inoue关于隧道磁电阻效应的理论得到的自旋极化率 P和 Co的原子百分数 x的关系曲线和实验测得的 RTMR ～ x曲线具有相似的变化趋势 .表明在 Fe Co- Si O2 膜中由于磁性颗粒自旋极化率 P的提高而使 RTMR 变大 .这也和基于第一原理的线性缀加平面波方法得到的理论计算结果一致 .

Fe φ-SiO 2 granular films were fabricated by rf sputtering (φ represents the Fe volume fraction). The microstructure of the film,its magnetic properties and tunneling magnetoresistance effect (TMR) were systematically studied. It is found that the maximum ratio of R TMR is about 3.3% as the metal volume fraction φ=0.33. Under the same conditions a series of (Fe 100-x Co x) 0.33 (SiO 2) 0.67 were prepared. The value of R TMR becomes -4.3% when x=53, but the microstructure is kept unchanged. We contribute a higher R TMR to the elevation of the spin polarization of particles,which is still consistent with our calculated result.