Zeit- und ortsaufgelöste Beobachtung von Magnetisierungsdynamik unter Verwendung von "Spin-polarized low energy microscopy" (SP-LEEM)

使用自旋偏振低能显微镜 (SP-LEEM) 对磁化动力学进行时间和空间分辨观察

• 批准号: 5372862
• 负责人: Professor Dr. Hans-Joachim Elmers
• 金额: --
• 依托单位: Institut für Physik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2002
• 资助国家: 德国
• 起止时间: 2001-12-31 至 2004-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5372862?language=en
• 关键词: Zeit; und; ortsaufgel; ste; Beobachtung

We will exploit the magnetisation dependence of the backscattering cross section of spin-polarised electrons providing both a high intensity of reflected electrons and a high asymmetry. Using an emission electron microscope we are able to image magnetic domains with high lateral resolution of better than 25 nm. A basic advantage of the technique is that it combines the highly resolving magnetic imaging with structural imaging including even the visibility of single monoatomic steps on surfaces. Time resolution is implemented by a stroboscopic illumination of the sample by a pulsed electron beam which in turn is produced by shining a pulsed laserbeam from a laserdiode on a GaAs-photocathode. The time resolution is limited by the pulse length of the electron beam pulse. Ultrafast magnetisation dynamics will be initiated in the sample either by application of field pulses using the strip-line technique or heating pulses using a Ti-sapphire laser. We will investigate single crystalline ultrathin magnetic films prepared by molecular beam deposition in situ in UHV. Strip-lines are lithographically prepared on a sapphire(11-20) substrate from a single crystalline Mo(110) film. The strip-line surface will be cleaned in UHV applying oxygen - anneal/flash cycles in order to allow for an epitaxial growth of ultrathin Co and Fe films. The dynamical magnetisation process will be investigated as a function of the time delay between field and/or heating pulse with respect to the electron probe pulse.

我们将利用自旋极化电子的背散射截面的磁化依赖性，提供高强度的反射电子和高不对称性。使用发射型电子显微镜，我们能够图像磁畴具有高的横向分辨率优于25纳米。该技术的一个基本优点是，它结合了高分辨率的磁成像与结构成像，甚至包括表面上单个单原子台阶的可见性。时间分辨率是通过脉冲电子束对样品的频闪照明来实现的，脉冲电子束又是通过将来自激光二极管的脉冲激光束照射在GaAs光电阴极上来产生的。时间分辨率受到电子束脉冲的脉冲长度的限制。超快磁化动力学将在样品中开始通过应用场脉冲使用的带状线技术或加热脉冲使用钛蓝宝石激光器。我们将研究在超高真空下用分子束原位沉积法制备单晶磁性薄膜。在蓝宝石（11-20）衬底上用光刻法从单晶Mo（110）膜制备带状线。将在超高真空中应用氧气退火/闪光循环来清洁带状线表面，以允许外延生长的Co-Co和Fe膜。动态磁化过程将作为场和/或加热脉冲相对于电子探针脉冲之间的时间延迟的函数进行研究。