2012 年 36 巻 2 号 p. 109-115
Magnetic force microscope (MFM) tips were prepared by coating Si tips of 5 nm radius with 3d ferromagnetic transition metals (Ni, NiFe, Fe, and Co). The effects of coated-film thickness and coating material on the MFM signal sensitivity and resolution were investigated. As the film thickness increases, the sensitivity increases due to the increase of magnetic volume of tip. Higher sensitivity is observed for the same film thickness in the order of tip coated with material with higher remanent magnetization, Ni < NiFe < Fe < Co. Resolutions of 14.0, 13.4, 10.6, and 9.1 nm are obtained with tips coated with 40-nm-thick Ni, 40-nm-thick NiFe, 20-nm-thick Fe, and 20-nm-thick Co films, respectively. As the film thickness further increases, the resolution decreases due to the increase of tip radius. The MFM resolution is influenced by both the remanent magnetization of coating material and the tip radius. Bit lengths of around 28 nm of an HDD medium with 528 Gb/in2 area density are clearly observed by employing the tips coated with 20-nm-thick Fe and 20-nm-thick Co films. A positioning technique of MFM observation of a same area for high-density magnetic recording media is also proposed.