论文标题
通过优化TA缓冲层来改善MNN/COFEB交换偏置系统的热稳定性
Improving thermal stability of MnN/CoFeB exchange bias systems by optimizing the Ta buffer layer
论文作者
论文摘要
我们研究了TA缓冲层对多晶/ MNN/ COFEB交换偏置系统的热稳定性的影响，显示在室温下高约1800 OE的高交换偏置。这些三层系统的热稳定性受到退火过程中发生的氮扩散的限制。大多数氮都扩散到TA缓冲层中，这对于MNN的良好晶体生长是必需的，因此是交换偏置系统的关键组成部分。为了提高热稳定性，我们准备了交换偏置堆栈，在该堆栈中我们改变了TA厚度，以寻找最佳值，以确保在较大的温度范围内稳定且高交换。我们的发现表明，2-5 nm TA的薄层确实支持稳定的交换偏置，直到退火温度超过$ 550^{\ circ} $ c。此外，我们发现引入tan $ _ {\ text {x}} $层之间的MNN和TA（充当屏障）可以防止氮扩散。但是，我们的结果表明，即使在热稳定性方面有益，这些度量也常常导致结晶度降低，从而降低交换偏差。
We investigated the influence of the Ta buffer layer on the thermal stability of polycrystalline Ta/ MnN/ CoFeB exchange bias systems, showing high exchange bias of about 1800 Oe at room temperature. The thermal stability of those trilayer systems is limited by nitrogen diffusion that occurs during annealing processes. Most of the nitrogen diffuses into the Ta buffer layer, which is necessary for good crystal growth of MnN and thus a crucial component of the exchange bias system. In order to improve the thermal stability, we prepared exchange bias stacks where we varied the Ta thickness to look for an optimum value that guarantees stable and high exchange over a broad temperature range. Our findings show that thin layers of 2-5 nm Ta indeed support stable exchange bias up to annealing temperatures of more than $550^{\circ}$C. Furthermore, we found that the introduction of a TaN$_{\text{x}}$ layer between MnN and Ta, acting as a barrier, can prevent nitrogen diffusion. However, our results show that those measures, even though being beneficial in terms of thermal stability, often lead to decreased crystallinity and thus lower the exchange bias.
