Optimization of high-frequency magnetic force microscopy by ferrite-coated cantilevers

High-frequency magnetic force microscopy (HF-MFM) is, e.g., employed for the analyses of harddisk write heads. To improve the performance of HF-MFM, we developed and analyzed cantilevers coated by (Ni, Zn) ferrites. The magnetic coatings were prepared by RF sputtering with a typical thickness of 50 nm. We systematically compared the HF-MFM images of harddisk write heads obtained by ferrite- and CoCr-coated cantilevers. The ferrite-coated cantilevers were found to produce increased HF-MFM signals up to the GHz regime, whereas the contrast in the images taken by the conventional CoCr-coated cantilevers appear to be strongly reduced at frequencies above 400 MHz. The improvement of the HF-MFM performance due to the ferrite-coated cantilevers is discussed by considering the specific imaging mechanism.