Simulation of high-resolution MFM tips for high-density magnetic recording media with low bit aspect ratio

To design the high-resolution magnetic force microscopy (MFM) tips suitable for high-density magnetic recording media with low bit aspect ratio (BAR), the transfer functions of tips with various sharpened tip-ends were calculated for a checkered perpendicular magnetization pattern and the resolution of these tips was estimated by considering the resolution limit due to thermal noise at room temperature. The cylindrical tip with a spheroidal tip-end having a large ellipticity is found to be a suitable candidate for high-resolution MFM imaging of magnetic recording media with low BAR. For the tips with ellipticities larger than tan 45°, there are no zero-signal frequencies. The sensitivity shows a maximum around an ellipticity of tan 70°. The spheroidal tip shows a much smaller tip thickness dependence compared to the bar shape tip with a flat tip-end or an ellipsoidal tip-end, because only the tip-end mainly contributes to signals in case of the spheroidal tip.