Abstract
Magnetic force microscope (MFM) tips are prepared by coating Si tips of 4 nm radius with Co and Fe65 Co35 (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.
Highlights
Magnetic force microscopy (MFM) has been widely used to investigate nano-scale magnetization structures of magnetic devices like hard-disk-drive (HDD) media
It was found that the resolution was influenced by the tip radius and by the signal detection sensitivity which depended on coating magnetic material
The Si tip of 4 nm radius, which is much smaller than the coating film thickness, was employed as a base-tip to reduce an influence of base-tip radius on the radius of tip after film coating
Summary
Magnetic force microscopy (MFM) has been widely used to investigate nano-scale magnetization structures of magnetic devices like hard-disk-drive (HDD) media. MFM tips are generally prepared by coating non-magnetic sharp tips with magnetic materials. The resolution of commercially available MFM tip is limited at around 20 nm. Various methods, such as reducing MFM tip radius using a focused ion beam, employment of a carbon nanotube, one-side coating of non-magnetic tip with magnetic material, etc. In our previous studies [14]–[18], MFM tips were prepared by coating Si tips with various magnetic materials of Fe, Co, Ni, Ni-Fe, Fe-B, Co-Cr-Pt, FePt, FePd, and CoPt. Resolutions better than 10 nm were obtained by selecting the coating material. It was found that the resolution was influenced by the tip radius and by the signal detection sensitivity which depended on coating magnetic material. The influence of coating thickness on the MFM spatial resolution is systematically investigated
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