Visualization of vortex core polarity in NiFe nanodots by tilted Fresnel images

► The sense of polarity appears as a bipolar white-black contrast in the difference image. ► It allows determining a core diameter of 16.5±2.5 nm as commonly seen in NiFe nanodots. ► Difference image in misaligned case shows characteristic behavior of bipolar contrast. ► Method is direct interpretation, resolution-free effect and more quantitative quantification.