Improvement of spin-torque oscillator with magnetic vortex and inter-layer coupling

自旋扭矩振荡器是下一代GHz以上低功耗高频振荡器的候选振荡器之一。其中一个实际问题是热稳定性，因为自旋扭矩振荡器很小。我们的目的是提高具有磁涡旋和交换耦合铁磁层的自旋扭矩振荡器的热稳定性。首先，我们提出了一种新的方法来评价铁磁层中磁涡的热稳定性。这种方法使我们能够绘制出铁磁点中的磁涡势。我们还成功地制作了具有磁涡旋的自旋扭矩振荡器。与传统的自旋扭矩振荡器相比，它具有更高的Q值，这是因为它具有更高的热稳定性。利用这些技术，我们可以评估具有交换耦合铁磁层的自旋扭矩振子。

Spin torque oscillator is one of the candidates for next generation oscillator with low power consumption and high frequency, over GHz. One of the practical problem is thermal stability because spin torque oscillator is small. Our purpose is to improve thermal stability of spin torque oscillator with magnetic vortex and exchange coupled ferromagnetic layer. At first, we developed novel method to evaluate thermal stability of magnetic vortex in ferromagnetic layer. This method allowed us to map the potential for magnetic vortex in ferromagnetic dot. We also succeeded to fabricate spin torque oscillator with magnetic vortex. It showed higher Q-value compared with that of conventional spin torque oscillator due to its higher thermal stability. Using these technique, we could evaluate spin torque oscillator with exchange coupled ferromagnetic layers.