Magnetic force microscope (MFM) tips are prepared by coating Si tips of 4 nm radius with CoPt-alloy films at 300 ℃ varying the thickness in a range between 10 and 200 nm. L11 ordered phase formation is recognized for the CoPt film. The influences of coating thickness on the spatial resolution and the switching field of MFM tip are investigated. With increasing the thickness from 10 to 30 nm, the resolution improves from 10.2 to 7.3 nm due to anincrease of signal detection sensitivity related with the remanent magnetization (Mrt) of coated film. As the thickness further increases, the resolution decreases due to an increase of tip radius. The resolution is influenced by both the detection sensitivity and the tip radius. The switching field monotonically increases from 1.7 to 5.8 kOe with increasing the thickness from 10 to 200 nm. High switching fields are obtained, which are interpreted to be reflecting the magnetocrystalline anisotropy of L11 ordered phase included in CoPt film. An MFM tip coated with CoPt film including L11 ordered phase is useful for the observation of magnetic domain structures of future HDD media and permanent magnets.
2013 The Magnetics Society of Japan