Preparation of high-resolution magnetic force microscope tips coated with Co and FeCo films

Magnetic force microscope (MFM) tips are prepared by coating Si tips of 4 nm radius with Co and Fe65Co35 (at. %) films by employing an ultra-high vacuum evaporation system. The effect of coating film thickness on MFM spatial resolution is investigated. With increasing the thickness from 10 to 20 nm, the resolutions of Co- and FeCo-coated tips improve from 8.4 to 6.9 nm and from 7.5 to 6.6 nm, respectively. Better resolutions are obtained for the FeCo-coated tips, which is due to enhanced sensitivities related with the higher magnetic moment of FeCo material. As the coating thickness further increases, the resolutions deteriorate due to increase of tip radius. The resolution is affected by the detection sensitivity and the tip radius. Magnetic bits of a perpendicular medium recorded at 1800 kFCI (bit length: 14.1 nm) and 1900 kFCI (13.4 nm) are respectively distinguishable in the MFM images observed by using tips coated with Co and FeCo films.