Ultraschnelle Magnetisierungsprozesse in Mikro- und Nanomagneten

在20 ~ 100 ns的时间尺度上，研究了微微米和亚微米尺寸的自旋阀薄膜元件在极快磁场脉冲下的动态响应。场脉冲将由电流脉冲通过微带线产生，或者通过向肖特基二极管泵送飞秒激光脉冲来产生。利用快速数字采样示波器测量巨磁阻，观察磁化进动和开关。主要研究采用分子束外延法生长的含有高结构完善的Fe1-xCox外延铁磁层的样品；这些薄膜的磁各向异性可以通过厚度和成分的变化在很宽的范围内控制，从而允许用众所周知的参数值进行实验，进入微磁模拟。研究了各向异性、温度与居里温度的关系以及交换耦合对第二铁磁层的影响。在与第二个研究小组的联合实验中，GMR信号将与时间分辨扫描克尔显微镜图像同时捕获，以结合这些互补方法的优势。

The dynamic response of micro- und sub-micrometer-size spinvalve film elements on very fast magnetic field pulses will be studied on a time scale of 20 ps to 100 ns. Field pulses will be created by current pulses through micro strip-lines and alternatively by pumping a Schottky diode with femtosecond laser pulses. Magnetization precession and switching will be observed by measuring the giant magnetoresistance with a fast digital sampling oscilloscope. Mainly samples will be studied containing an epitaxial ferromagnetic Fe1-xCox free layer of high structural perfection grown by molecular beam epitaxy; magnetic anisotropies of these films are controlled in a wide range by variation of thickness and composition thus allowing experiments with well-known values of the parameters entering micromagnetic simulations. The influence of anisotropies, of temperature in relation to the Curie temperature and of exchange coupling to a second ferromagnetic layer will be investigated. In a joint experiment with a second research group the GMR signal will be captured simultaneously with a time-resolved scanning Kerr microscopy image to combine the advantages of these complementary methods.