The read-back signal degradation in seek motion with a pseudo-contact head in a hard disk drive was studied. It was found by AES analysis that the pole tip surface of NiFe was covered with a decomposed layer of NiFe and carbon following seek motion. The read-back signal degradation became larger with increasing thickness of the decomposed layer. An MFM study of the seek-tested pole tip surface showed that the magnetic properties of the pole tip surface deteriorated by seek motion, and that the read-back signal degradation increased with increase of deterioration of the magnetic properties of the pole tip surface. These results suggest that either the poor permeability of the decomposed layer on the pole tip surface and increase of spacing between the fresh pole tip surface under the decomposed layer and the disk surface decrease the flux flow from the disk magnetic layer into the pole tip, or that the decomposed layer on the gap short-circuits the flux flow. It was found that the additive, cyclotriphosphazene, in a lubricant film, and a protective layer of carbon on a slider surface drastically reduced degradation.