Chen Yuan-Tsung, Lin Sung-Hao, Sheu Tzer-Shin
Department of Materials Science and Engineering, I-Shou University, Kaohsiung 840, Taiwan.
Nanomaterials (Basel). 2014 Jan 2;4(1):46-54. doi: 10.3390/nano4010046.
In this investigation, the low-frequency alternate-current (AC) magnetic susceptibility (χ) and hysteresis loop of various MgO thickness in CoFeB/MgO/CoFeB magnetic tunneling junction (MTJ) determined coercivity () and magnetization () and correlated that with χ maxima. The multilayer films were sputtered onto glass substrates and the thickness of intermediate barrier MgO layer was varied from 6 to 15 Å. An experiment was also performed to examine the variation of the highest χ and maximum phase angle (θ) at the optimal resonance frequency (), at which the spin sensitivity is maximal. The results reveal that χ falls as the frequency increases due to the relationship between magnetization and thickness of the barrier layer. The maximum χ is at 10 Hz that is related to the maximal spin sensitivity and that this corresponds to a MgO layer of 11 Å. This result also suggests that the spin sensitivity is related to both highest χ and maximum phase angle. The corresponding maximum of χ is related to high exchange coupling. High coercivity and saturation magnetization contribute to high exchange-coupling χ strength.
在本研究中，通过测量CoFeB/MgO/CoFeB磁性隧道结（MTJ）中不同MgO厚度的低频交变电流（AC）磁化率（χ）和磁滞回线，确定了矫顽力（）和磁化强度（），并将其与χ最大值相关联。多层膜被溅射在玻璃基板上，中间势垒MgO层的厚度在6至15埃之间变化。还进行了一项实验，以研究在最佳共振频率（）下最高χ和最大相角（θ）的变化，此时自旋灵敏度最大。结果表明，由于磁化强度与势垒层厚度之间的关系，χ随频率增加而下降。最大χ出现在10 Hz，这与最大自旋灵敏度相关，且对应于11埃的MgO层。该结果还表明，自旋灵敏度与最高χ和最大相角均有关。χ的相应最大值与高交换耦合有关。高矫顽力和饱和磁化强度有助于提高交换耦合χ强度。
