Multiple neuromorphic applications require the tuning of two or more devices to a common signal. Various types of neuromorphic computation can be realized using spintronic oscillators, where the DC current induces magnetization precession, which turns into an AC voltage generator. However, in spintronics, synchronization of two oscillators using a DC signal is still a challenging problem because it requires a certain degree of similarity between devices that are to be synchronized, which may be difficult to achieve due to device parameter distribution during the fabrication process. In this work, we present experimental results on the mechanisms of synchronization of spin-torque oscillators. Devices are based on magnetic tunnel junction with a perpendicularly magnetized free layer and take advantage of a uniform magnetization precision in the presence of the magnetic field and a DC bias. By using an external microwave source, we show the optimal condition for the synchronization of the magnetic tunnel junctions. Finally, we present results on the in-series connection of two junctions and discuss the possible path towards improving oscillation power and linewidth. In addition, using numerical simulations of the coupled oscillators model, we aim to reproduce the conditions of the experiments and determine the tolerance for achieving synchronization.

翻译：多种神经形态应用需要将两个或多个器件调谐至同一信号。利用自旋电子振荡器可实现多种类型的神经形态计算，其中直流电流激发磁化进动，进而转化为交流电压发生器。然而在自旋电子学中，利用直流信号同步两个振荡器仍具挑战性，因为要求待同步器件具有一定程度的相似性，而制造过程中的器件参数分布可能导致该条件难以满足。本工作展示了自旋扭矩振荡器同步机制的实验研究成果。器件基于具有垂直磁化自由层的磁性隧道结，并利用磁场与直流偏置下均匀磁化进动的优势。通过使用外部微波源，我们揭示了磁性隧道结同步的最优条件。最后，我们展示了两个结串联连接的结果，并讨论了提升振荡功率与线宽的潜在路径。此外，基于耦合振荡器模型的数值模拟，我们旨在复现实验条件并确定实现同步的容差范围。