垂直磁记录介质中飞秒激光诱导的磁性软化研究

项目名称： 垂直磁记录介质中飞秒激光诱导的磁性软化研究

项目编号： No.50871030

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 轻工业、手工业

项目作者： 周仕明

作者单位： 同济大学

项目金额： 45万元

中文摘要： 本项目采用时间分辨的极向磁光效应，研究垂直磁记录介质中磁化强度和磁化翻转机理随延迟时间(亚皮秒范围)的演变过程。(1)针对L1(0)FePt-Ag, L1(0)FePt, and L1(0)FePt-MgO三种不同的样品，研究其泵浦光作用下的磁性软化现象。结果发现，软化现象依次逐渐变得明显。这是由于在这三个样品中FePt吸收的光子能量逐渐增加， 这个结果有助于飞秒辅助超高密度磁记录设计。（2）为了揭示磁性软化的物理本质，我们设计了单脉冲泵浦技术。对于FePt 有序合金薄膜，单脉冲作用下的磁滞回线在任何延迟时间下，矫顽力和静态都相同，结果对任何泵浦脉冲功率都成立。清楚表明，多脉冲情况下的磁性软化现象来源于磁化翻转的积累效应，同时在泵浦光作用下，样品的磁各向异性保持不变。（3）在不同脉冲数的情况下测量了GdFeCo垂直薄膜的一系列反常磁滞回线，发现其磁滞回线从单脉冲到多脉冲的演变过程，进一步确认记忆和累积效应。

中文关键词： 垂直磁记录；磁超快；自旋动力学；飞秒激光

英文摘要： (1) In this project, we use the time-resolved magneto-optical polar Kerr effect technique to study the transient magnetization and magnetization reversal mechanism as a function of the time-delay. As for Ag-L1(0)FePt, L1(0) FePt alloy films, and MgO-L1(0) FePt films, we found that at specific light fluence, the magnetic softening becomes more serious in the same order. This is because the absorption of L1(0)FePt component is enhanced in the same order. This work is helpful for the designing of the next generation femtosecond laser assisted ultrahigh magnetic recording technique.(2) In order to reveal the nature of magnetic softening, we have measured the hysteresis loops upon application of single femtosecond laser pulse. we found that the coercivty almost does not change upon application of femtosecond laser. It is indicated that the perpendicular magnetic anisotropy almost does not change. For GdFeCo films, we have measured the hysteresis loop for different numbers of pumping laser pulse. We can find that the evolution of hysteresis loop shape from single pulse to multi-pulse. In this way, the memory and accumulation effects are identified.

英文关键词： perpendicular magnetic recording; magnetic ultrafast; spin dynamics; femto laser