Optically-induced magnetization reversal of coupled zero moment ferrimagnets and synthetic ferrimagnets

提出的研究项目的目的是探索全光开关作为一种新的方法来实现超快磁化反转的潜力，这对未来的信息处理技术非常重要。对数字数据存储的永无止境的需求仍然是硬盘驱动器不断增加的面密度、更大的容量和更好的性能的驱动力。然而，磁数据存储和信息处理的速度对设备性能特别重要，但目前仅限于几纳秒。因此，对提高信息存储速度的需求引发了激烈的研究活动，以寻找在超短时间尺度上控制磁化的方法。在这方面，最近在亚铁磁性稀土-过渡金属(RE-TM)合金薄膜中观察到了由圆偏振飞秒激光脉冲诱导的超快磁化反转过程，其中开关的方向取决于在没有任何外加磁场的情况下光的螺旋度。然而，全光开关中潜在机制的许多基本方面还没有被理解，需要更多的实验努力来揭示所涉及的基本物理。全光开关这一复杂的科学挑战是拟议研究项目的重点，包括各种新的材料系统，如零净磁矩的耦合亚铁磁异质结构以及基于反铁磁耦合铁磁层的合成亚铁磁体。

The aim of the proposed research project is to explore the potential of all-optical switching as a novel approach to ultra-fast magnetization reversal important for future information processing technology. The insatiable demand for digital data storage is still the driving force for ever increasing areal density, larger capacities and better performance of hard disk drives. However, the speed of magnetic data storage and information processing is particularly important for device performance, but presently limited to a few nanoseconds. Thus the demand for increasing speed of information storage has triggered intense research activities for finding ways to control the magnetization at ultrashort time scales. In this regard, ultra-fast magnetization reversal processes induced by circular polarized femto¬second laser pulses was observed recently in ferrimagnetic rare earth-transition metal (RE-TM) alloy thin films, where the direction of the switching is determined by the helicity of the light in the absence of any external applied magnetic fields. However, many fundamental aspects of the underlying mechanism in all-optical switching are not yet understood, and additional experimental efforts are required to reveal the fundamental physics involved. This complex scientific challenge of all-optical switching is in the focus of the proposed research project including various novel material systems such as coupled ferrimagnetic heterostructures with zero net moment as well as synthetic ferrimagnets based on antiferromagnetically coupled ferromagnetic layers.