Development of method of high resolution magnetic imaging by spin polarized scanning tunneling microscope

为了高分辨率地研究表面的磁性，我们研制了自旋极化扫描隧道显微镜（SP-STM）。首先，我们制作了一个超高真空（UHV）系统，包括一个分析室和一个准备室，分析室配备了一个最大磁场为8 kOe的电磁铁，STM和低电子能量衍射和俄歇电子能谱（LEED/AES）系统。超高真空系统采用机械旋转泵、涡轮分子泵、离子泵和钛升华泵抽真空，在150 ℃烘烤后，真空度达到1 × 10 ^<-8>0 Pa。扫描隧道显微镜由管状压电陶瓷扫描器、航向压电马达、抗振螺旋弹簧、样品保持器和测量隧道电流的前置放大器组成。使用摇摆棒更换ASTM头端。四个STM吸头和两个样品储存在分析室内的转盘中。我们用数字控制方法研制了STM控制器。通过前置放大器对针尖和样品之间的隧穿电流进行转换，得到的电压由16位AD转换器读取，AD转换器用于数字反馈控制针尖从样品的位置。通过向压电扫描器的X和Y电极施加三角电压来实现扫描。为了测量自旋极化信息，使用放大器中的岩石来检测隧穿电流的AC分量。为了制备用于SP-STM测量的磁性纳米结构样品，采用AFM阳极氧化法对坡莫合金Ni_ Fe_（1-x）薄膜进行了制备<80><20>。在本研究中，我们开发了SP-STM。接下来，我们将利用该测量系统来获取纳米尺度下的表面磁信息。

We developed spin polarized scanning tunneling microscope (SP-STM) in order to investigate magnetic properties on surfaces with high resolution. First, we fabricated an ultra-high vacuum (UHV) system that consists of an analysis chamber and a preparation chamber; the analysis chamber equips an electromagnet with maximum magnetic field of 8 kOe, the STM and a low electron energy diffraction and auger electron spectroscopy (LEED/AES) system. The UHV system is evacuated by mechanical rotary pump, turbo molecular pump, ion pump and titanium sublimation pump; after baking this chamber at temperature of 150 degrees, vacuum pressure of lx10^<-8>0 Pa was obtained. The STM consists of a scanner of a tube piezo ceramics, a piezo motor for course approach, coil springs for anti-vibration, a sample holder and a pre-amplifier for measurement of tunneling current. ASTM tip is exchanged by using a wobble stick. Four STM tips and two samples are stored in a carousel inside the analysis chamber. We developed an STM controller with digital control method. A tunneling current flowing between tip and sample is converted by the pre-amplifier, and the obtained voltage is read by 16 bits AD converter, which is used for digital feedback to control the tip position from the sample. Scanning was achieved by applying triangular voltages to X and Y electrodes of the piezo scanner. For measuring spin polarized information, a rock in amplifier was used to detect AC components of the tunneling current. In order to fabricate sample of magnetic nano-structure for SP-STM measurements, fabrication by AFM anodization was performed on the permalloy Ni_<80>Fe_<20> thin film. In this study we developed the SP-STM. Hereafter, we will use this measurement system to obtain the surface magnetic information in nano-scale.