Observation of stray fields from hard-disk writer poles up to 2 GHz

By means of high-frequency magnetic force microscope (HF-MFM) the emanating stray fields from hard-disk writer poles are measured at carrier frequencies up to 2 GHz. For the present measurements, hard-disk writer poles stemming from SEAGATE were employed. At 1000 MHz and above, the field directly at the gap is dominating, while the fields along the downtrack direction are found to decrease. The observation of the stray fields at these high frequencies is only possible by employing MFM cantilevers with a 50-nm-thick (Ni,Zn)-ferrite coating. We show that the use of these tips gives much larger signal than those obtained by conventional CoCr-coated cantilevers.