School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Ultramicroscopy. 2011 Jul;111(8):1276-85. doi: 10.1016/j.ultramic.2011.04.002. Epub 2011 Apr 14.
We illustrate an approach which allows determining the out-of-plane component of the vortex core (polarity) in NiFe nanodots using Fresnel imaging in Lorentz electron microscopy. Using tilted Fresnel images, contribution of the polarity is introduced into the Fresnel image. However, this contribution is relatively small and a difference image from two symmetrically tilted Fresnel images must be used to eliminate the strong contribution from the in-plane curling magnetization and non-magnetic contrast. The sense of the polarity appears as a bipolar white-black contrast in the difference image on the tilt axis. A vortex core with a diameter of 16.5 ± 2.5 nm is experimentally measured. Image tilting, displacement and geometrical distortion may disturb the difference image, and hence subtraction of the difference image must be aligned by cross-correlation. The method is also justified by a study of the observed contrast characteristic due to misalignment. The method is confirmed to be superior to similar approach with direct interpretation of information and more information subtracted.
我们展示了一种方法，通过洛伦兹电子显微镜中的菲涅耳成像来确定 NiFe 纳米点中涡旋核的面外分量（极性）。使用倾斜菲涅耳像，极性的贡献被引入到菲涅耳像中。然而，这种贡献相对较小，必须使用来自两个对称倾斜菲涅耳图像的差分图像来消除来自面内卷曲磁化强度和非磁性对比度的强烈贡献。在倾斜轴上的差分图像中，极性的方向表现为双极黑白对比。实验测量了直径为 16.5 ± 2.5nm 的涡旋核。图像倾斜、位移和几何变形可能会干扰差分图像，因此必须通过互相关对齐差分图像的减法。该方法还通过研究由于未对准而导致的观察到的对比度特征得到了验证。该方法被证实优于具有直接解释信息和更多信息相减的类似方法。
