Magnetic force microscope (MFM) tips are prepared by coating magnetic materials on nonmagnetic Si tips with 4 nm radius. The effects of magnetic material and coating thickness on the MFM resolution and the switching field are investigated. MFM resolutions better than 8 nm have been confirmed with tips coated with soft magnetic or hard magnetic materials with optimized thicknesses. The switching field varies in a wide range 0.1-3.0 kOe depending on the coating material and the coating thickness (10-80 nm). High-resolution MFM tips are applied to the observations of magnetization structures of perpendicular and bit-patterned media samples. Magnetization structures of less than 20 nm in scale are clearly observed.