Abstract
Magnetic force microscope (MFM) tips are prepared by coating Si tips of 4 nm radius with L 10 ordered FePd-alloy films varying the thickness in a range between 10 and 80 nm. The effects of coating thickness on spatial resolution and switching field of MFM tip are investigated. As the thickness increases from 10 to 20 nm, the MFM signal detection sensitivity is improved and the resolution improves from 12.7 to 7.9 nm. With further increasing the thickness, the resolution decreases due to increase of tip radius. Magnetic bits of 15.9 nm length of a perpendicular medium recorded at 1600 kilo-flux-change-per-inch are distinguishable in the MFM image observed by using a tip coated with 20-nm-thick FePd film. The switching field monotonically increases from 0.70 to 1.50 kOe with increasing the coating thickness from 10 to 80 nm. The present study has shown that it is possible to prepare an MFM tip with spatial resolution better than 10 nm and switching field higher than 1 kOe by coating a sharp Si tip with an L 10 ordered FePd-alloy film.
Highlights
Magnetic force microscopy (MFM) has been widely used to investigate the magnetization structures of magnetic devices like hard-disk-drive (HDD) media, permanent magnets, etc
MFM tips with high Hsw have been prepared by annealing tips coated with L10 ordered FePt- and CoPt-alloy films followed by focusedion-beam milling [6, 7]
Figures 2(a-1)–(c-1) show the scanning electron microscopy (SEM) images observed for a base-Si tip and of MFM tips coated with FePd(20 nm)/MgO(5 nm) and FePd(40 nm)/MgO(5 nm) films
Summary
Magnetic force microscopy (MFM) has been widely used to investigate the magnetization structures of magnetic devices like hard-disk-drive (HDD) media, permanent magnets, etc. MFM tips are generally prepared by coating non-magnetic sharp tips with magnetic materials [1]–[7]. The tip shape and the magnetic property of coated material influence the spatial resolution and the switching field (Hsw) of MFM tip. Future HDD media are considered to consist of magnetic materials with very high uniaxial magnetocrystalline anisotropy energies such as FePt and SmCo5. Realization of high Hsw is required in addition to highresolution better than 10 nm for MFM observations of such ultra-high-density media. MFM tips with high Hsw have been prepared by annealing tips coated with L10 ordered FePt- and CoPt-alloy films followed by focusedion-beam milling [6, 7]. The resolution of commercially available MFM tip coated with L10 ordered film is limited at around 20 nm
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