Effect of annealing temperature on formation of superparamagnetism in CoFeB/MgO/CoFeB magnetic tunnel junctions
Effect of annealing temperature on formation of superparamagnetism in CoFeB/MgO/CoFeB magnetic tunnel junctions
复制标题
退火温度对CoFeB/MgO/CoFeB磁隧道结超顺磁性形成的影响
DOI：
10.1016/j.apsusc.2014.07.015
复制
发表时间：
2014
影响因子：
6.7
通讯作者：
Freitas P. P.
中科院分区：
文献类型：
--
作者：
Cao Jiangwei;Liu Yan;Ren Yang;Wei Fulin;Freitas P. P.
我们报告了具有薄自由层的 CoFeB/MgO/CoFeB 磁隧道结的退火效应。对于 CoFeB 自由层低于临界厚度的结，MR 传输曲线始终无磁滞，并且 TMR 比率随着退火温度的升高而降低。对于CoFeB自由层在临界厚度以上的结，随着退火温度的升高，TMR比和矫顽力均先增大后减小，最终得到无磁滞的MR传输曲线。使用 Langevin 方程可以很好地拟合没有磁滞的 MR 环路，这表明在高温退火过程中自由层中形成了超顺磁性颗粒。这种行为源于超薄CoFeB自由层在退火过程中的转变：CoFeB的结晶过程以及MgO/CoFeB和CoFeB/Ru界面处的扩散。
We report the annealing effect of CoFeB/MgO/CoFeB magnetic tunnel junctions with a thin free layer. For the junctions with CoFeB free layer below the critical thickness, the MR transfer curves are always hysteresis-free and TMR ratio decreases with increasing annealing temperature. For the junctions with CoFeB free layer above the critical thickness, with increasing annealing temperature, both TMR ratio and coercivity increase firstly and then decrease, and finally hysteresis-free MR transfer curves are obtained. The MR loops without hysteresis can be well fitted by using the Langevin equation, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. This behavior originates from the transformation of the ultra-thin CoFeB free layer during annealing: crystallization process of CoFeB and diffusion at MgO/CoFeB and CoFeB/Ru interfaces.