Top-pinned soft magnetic underlayer with nano- or oriented-crystalline structure fabricated by electroless plating

To suppress both spike noise and wide adjacent track erasure for perpendicular recording media, we have proposed a soft magnetic underlayer (SUL) with the top-type pinning structure, which consists of a soft magnetic layer fabricated by plating and an antiferromagnetic layer deposited by sputtering, on an Al/NiP substrate (top-pinned plated SUL). To realize this concept, plated NiFe layers with random nano-crystalline structure and with (111) sheet texture were achieved using suitable reducers in electroless plating. Magnetic domain structures inside the whole disk for the top-pinned plated SUL prepared under various field-cool conditions reveal that the thermal stability of a single-domain state can be maintained over 130 °C even for a small antiferromagnetic layer thickness of 5 nm.