Search for the optimally suited cantilever type for high-frequency MFM

To optimize the performance of the high-frequency MFM (HF-MFM) technique [1-4], we performed a search for the best suited cantilever type and magnetic material coating. Using a HF-MFM setup with hard disk writer poles as test samples, we carried out HF-MFM imaging at frequencies up to 2 GHz. For HF-MFM, it is an essential ingredient that the tip material can follow the fast switching of the high-frequency fields. In this contribution, we investigated 6 different types of cantilevers, (i) the standard MFM tip (Nanoworld Pointprobe) with 30 nm CoCr coating, (ii) a SSS (Nanoworld SuperSharpSilicon^TM) cantilever with a 10 nm CoCr coating, (iii) a (Ni, Zn)-ferrite coated pointprobe tip, (iv) a Ba₃Co₂Fe₂₃O₄₁ (BCFO) coated pointprobe tip, (v) a low-coercivity NiCo alloy coated tip, and (vi) a permalloy-coated tip.