交换耦合复合结构的超快光磁调制及其机理研究

Laser-assisted magnetic recording which can not only overcome the limit of magnetic recording density but also shows great potential on recording speed, is one of the hot issues in recent domain of information-storing technology. Especially, to realize ultrafast recording, laser-induced ultrafast magnetization dynamics has attracted much attention. Moreover, exchange-coupled composite film is the excellent medium of ultrahigh-density magnetic recording because it has excellent heat-stability and its coercivity can be reduced meanwhile. In order to demonstrate the approach of realizing ultrafast and ultrahigh-density recording on such medium, it is significant to study the dynamically magnetic features of exchange-coupled composite film under the excitation of femtosecond laser. In this program, the behaviors and features of ultrafast photomagnetic modulation on exchange-coupled composite films, such as FePt/FeNi and FePt/Fe, will be studied by using the femtosecond time-resolved magneto-optical Kerr-effect spectroscopy. In addition, we will build a numerical model which is suitable for calculating the photomagnetic modulation on exchange-coupled composite structure, by introducing the laser-modulation effect base on the approaching of Landau-Lifshitz-Bloch (LLB) micromagnetics and the three-temperature model. This method has the advantage of intuitive and accuracy on analysing and explaining the experimental results, due to the direct calculation of the laser-induced magnetization-dynamics informations in time domain.

激光辅助磁记录既能克服磁记录的密度瓶颈，在记录速度上也显示出巨大潜力，是当今信息存储技术领域的热点课题之一。为实现超高速度的信息存储，激光感应的超快磁化动力学研究尤其广受关注。另一方面，交换耦合复合结构薄膜在具有优异热稳定性的同时，所需矫顽场也被有效降低，是超高密度磁记录的优选介质。为了深入探索在此类介质上实现超高密度、超高速度记录的途径，研究飞秒激光作用下交换耦合复合结构的动态磁特性具有重要意义。本研究拟运用飞秒时间分辨磁光克尔光谱技术，对FePt/FeNi、FePt/Fe等交换耦合复合结构薄膜的超快光磁调制行为及特性进行实验研究。同时，拟基于Landau-Lifshitz-Bloch(LLB)微磁学方法与三温度模型理论，引入激光调制作用，建立一套适用于交换耦合体系光磁调制的数值计算模型。本方法因从时域上直接计算获得激光感应的磁化动力学信息，故在分析和解释实验结果时具有直观、准确的优点。

为了探索在交换耦合复合结构薄膜上实现超高密度、超高速度光磁记录的途径，研究飞秒激光作用下该类介质的动态磁特性具有重要意义。本项目主要从实验和理论上对多种交换耦合复合结构薄膜以及相关铁磁薄膜的超快光磁调制行为、特性以及相关物理机制进行了研究。在磁化进动动力学特性与磁阻尼、交换耦合的激光调制、光脉冲诱导磁化偏转、自旋波模式及特性等几方面都取得了重要进展。研究成果对在交换耦合薄膜光磁记录中获得快速可控的写入窗口、实现局域磁化进行超快控制以及相关铁磁薄膜在磁基自旋电子技术中的应用等方面具有一定的指导意义。