具有SAF结构的IrMn基自旋阀材料的磁场退火研究

Effect of Magnetic Annealing on IrMn Based Spin Valve Materials with SAF Structure

用磁控溅射法制备了被钉扎层为反铁磁(SAF)结构(CoFe/Ru/CoFe)的IrMn基顶钉扎自旋阀材料,分别采用HRTEM、AFM、XPS对材料的结构和成分进行表征。首先,制备的自旋阀材料分别在200℃、245℃、255℃、265℃的真空条件(<10-5 Pa)下退火4 h,发现经265℃退火,自旋阀材料会发生明显的层间扩散,从而引起磁电阻率的降低。在选择合适退火温度(245℃)的基础上,研究了退火磁场对自旋阀材料磁电阻率的影响。在245℃的真空环境下,沿着材料的钉扎方向分别施加大小为80、160、240、400、560 kA/m的磁场退火4 h。实验发现经过80和160 kA/m的磁场退火后,材料的磁电阻率由退火前的8.80%分别下降到5.87%和6.31%;经240 kA/m的磁场退火后材料的磁电阻率变为7.91%;经400 kA/m的磁场退火后磁电阻率增大到9.89%;经560 kA/m的磁场退火后磁电阻率进一步增大到10.79%,比退火前增加了22.6%。

IrMn based spin valve materials with SAF （CoFe/Ru/CoFe） structure were deposited by magnetron sputtering system. HRTEM, AFM and XPS techniques were utilized to characterize the microstructures and composition of the spin valve materials. First, the deposited materials were annealed at 200℃, 245℃, 255℃ and 265℃ for 4 h in vacuum （〈 10-5 Pa）. It was found that obvious interlayer diffusion was happened after being annealed at 265 ℃, which resulted in the decrease of magneto-resistance （MR） ratio. Set field annealing temperature at 245 ℃, the spin valve materials were annealed at fields of 80, 160, 240, 400 and 560 kA/m along the pinning direction for 4 h in vacuum, respectively. It was found that the MR ratio of the materials declined to 5.87% and 6.31% from 8.80% after 80 kA/m and 160 kA/m annealing, respectively. After 240 kA/m annealing, the MR ratio became 7.91%. After 400 kA/m annealing, the MR ratio increased to 9.89%. After 560 kA/m annealing, the MR ratio reached 10.79%, which was increased by 22.6% as compared with the material before annealing.