Micromagnetic studies on resolution limits of magnetic force microscopy tips with different magnetic anisotropy

In magnetic force microscopy (MFM), it is effective to control the magnetic properties of the coating materials on the MFM tip to achieve higher resolution. In this work, the effect of the magnetic anisotropy of the tip-coating, such as perpendicular magnetic anisotropy (PMA), in-plane magnetic anisotropy (IMA), and random magnetic anisotropy (RMA), on the MFM image resolution are studied by micromagnetics. An accurate 3 D micromagnetic model of the CoPt pyramid MFM tip, with a cone angle of 37 degrees, tip height of 120 nm, coating thickness of 7.6 nm, and average grain size of about 8.8 nm, was setup to calculate the domain structure and the stray field of the tip. A CoPt disk medium, with a bit size of 24 x 32 nm(2) and film thickness of 8 nm, was chosen for image simulation. The PMA tip is advantageous in low scan height (SH) measurement with little tip-sample interaction due to its sharp and small stray field, while the IMA tip will disturb the magnetic moments of the medium at a low SH due to its strong stray field, and the RMA tip cannot read the bits with clear image contrast due to its broader field distribution. (C) 2012 American Institute of Physics. [doi:10.1063/1.3671785]