Bode M, Kubetzka A, Von Bergmann K, Pietzsch O, Wiesendanger R
Institute of Applied Physics, University of Hamburg, D-20355 Hamburg, Germany.
Microsc Res Tech. 2005 Feb;66(2-3):117-25. doi: 10.1002/jemt.20151.
In the past, spin-polarized scanning tunneling microscopy (SP-STM) was mainly applied to static domain configurations that do not vary in time. Here, we show that SP-STM may also be used to image the thermal switching behavior of superparamagnetic nanoislands. Special experimental care has to be taken in order to allow the unambiguous interpretation of the obtained data. Most important, the imaging of superparamagnetic particles requires the use of antiferromagnetic probe tips as the stray field of ferromagnetic tips may modify the sample's intrinsic switching behavior. Our results show that Fe monolayer islands on Mo(110) switch thermally when their area is smaller than 40 nm2. Dipolar coupling between adjacent islands is observed at small inter-particle distance. A pronounced shape dependence is found that confirms existing but yet unverified analytical predictions. The first experiments performed on Fe double-layer islands on W(001) also show thermal switching events, but no clear-cut size dependence is found.
过去，自旋极化扫描隧道显微镜（SP-STM）主要应用于不随时间变化的静态畴结构。在此，我们表明SP-STM也可用于对超顺磁性纳米岛的热开关行为进行成像。为了能对所获数据进行明确解读，必须采取特殊的实验措施。最重要的是，超顺磁性颗粒的成像需要使用反铁磁探针尖端，因为铁磁尖端的杂散场可能会改变样品的固有开关行为。我们的结果表明，当Mo(110)上的铁单层岛面积小于40 nm2时会发生热开关。在小颗粒间距下观察到相邻岛之间的偶极耦合。发现了明显的形状依赖性，这证实了现有的但尚未得到验证的分析预测。在W(001)上的铁双层岛上进行的首次实验也显示出热开关事件，但未发现明确的尺寸依赖性。
