Femtosecond switching and reading of magnetic vortex memory devices

我们的现代网络社会不断要求更小更快的存储设备，目前限制在GHz的读写速度（STT-MRAM）。达到下一阶段——太赫兹区——的一种方法是利用光子学。我们提出了一种磁光概念，可以提供这两种方法，证明所需的磁开关在太赫兹频率下工作的原理，以及以所需的飞秒时间和纳米尺度空间分辨率理解这一过程。我们研究的飞秒磁化开关的纳米磁性结构是薄铁磁盘的磁涡核。当磁化在这个地核周围循环时，在它的中心，磁化不是指向“上”就是指向“下”。它们的尺寸~ 10nm和完美的稳定性使它们成为在太赫兹频率下工作的磁性数据存储器件的有希望的候选者。实验上，我们将继续进行模拟，预测半周期MV/cm太赫兹脉冲的磁场可以用于这些涡旋核的飞秒自旋开关。为了将这种切换步骤与涡旋核心中心所需的空间定位读取步骤结合起来，太赫兹脉冲将与飞秒x射线脉冲同步，聚焦到纳米级。这将使自旋动力学成像，从而在太赫兹频率的磁化开关。为了在太赫兹频率下观察这种磁开关，我们将使用圆偏振fs x射线，应用一种称为x射线磁圆二色性（XMCD）的技术。通过比较左右圆极化脉冲在特定吸收边的传输，可以得到垂直于涡旋核心平面的磁化分量。该项目将与MPB通信公司和由以色列理工学院和庆应大学的国际合作者支持的少数周期公司合作，开发一种颠覆性的磁光技术，使磁涡流存储设备的飞秒开关和读取成为可能，以扩展下一代数据存储设备的性能。

Our modern networked society keeps asking for smaller and faster memory devices, which are currently limited to GHz reading and writing speed (STT-MRAM). One way to reach the next stage, the THz regime, is using photonics. We present a magneto-optical concept that can provide both, proof of principle that the required magnetic switching works at THz frequencies, as well as understanding the processes with the required femtosecond temporal and nanoscale spatial resolution. The nanofabricated magnetic structure we will investigate for femtosecond magnetization switching is the magnetic vortex core of thin ferromagnetic discs. While magnetization circulates around this core, at its center the magnetization points either "up" or "down". Their size ~10 nm and perfect stability make them promising candidates for magnetic data storage devices operated at THz frequencies. Experimentally, we will follow simulations which have predicted that the magnetic field of a half-cycle MV/cm THz pulse could be used for femtosecond spin switching of these vortex cores. To combine this switching step with the required spatially localized reading step at the center of the vortex core, the THz pulse will be synchronized with a femtosecond X-ray pulse, focussed down to the nanoscale. This will enable to image the spin dynamics and thus the switching of magnetization at THz frequencies. To observe this magnetic switching at THz frequencies, we will use circularly polarized fs X-rays, applying a technique called X-ray magnetic circular dichroism (XMCD). By comparing the transmission between left and right circularly polarized pulses at specific absorption edges, one can retrieve the magnetization component normal to the plane of the vortex core. This project will enable the development of a disruptive magneto-optical technology that enables femtosecond switching and reading of magnetic vortex memory devices in collaboration with MPB Communications Inc. and few-cycle Inc., supported by international collaborators from Technion and Keio University, to scale the performance of the next generation of data storage devices.