Magnetic force microscopy of recording media (abstract)

Abstract

Magnetic force microscopy (MFM) is an imaging technique which is particularly well suited to studying magnetization patterns and other issues in magnetic recording physics. The technique provides high magnetic contrast, submicrometer resolution, requires a minimum of sample preparation, and can be used with both soft and hard magnetic materials. We have developed a MFM designed around a novel optical-fiber interferometer incorporating a laser diode, and have used it to study a variety of thin films of recording media. We have imaged transitions written with a recording head in both CoPtCr, a longitudinal medium in which the magnetization lies in plane, and CoCr, a perpendicular medium. The MFM revealed fine structure such as intrinsic media noise on virgin media, detail within magnetic transitions, and side-writing effects. We have also used the MFM to study the erase band created during overwrite under various conditions. In films of SmCo, a novel thin-film medium, the MFM revealed that there exists a minimum spacing between transitions below which the magnetization pattern cannot be sustained. In order to improve lateral imaging resolution, we have fabricated tips by sputter coating nonmagnetic tungsten tips with 50 nm of CoPtCr. Using these tips we have achieved resolution well under 100 nm.