選択化学エッチング法による無電解ＣｏＮｉＰ垂直磁気記録媒体の微細偏析構造の解析

Abstract

The segregated microstructures of electrolessdeposited CoNiP perpendicular magnetic recording media with various Hc (⊥) of 500, 1000 and 1500 Oe were investigated by using the selective chemical etching technique; Co-rich ferromagnetic regions were preferentially dissolved with an etchant of sodium hydroxide-m-nitrobenzenesulfonic acidethylenediamine aqueous solution. TEM observation of the etched 1500 Oe film revealed an “asteroid“ pattern with hexa-symmetry, which was expected to be a substructure with a Ni-rich composition. It is considred that the Co-rich regions are segregated between the “arms” of the asteroid substructure. The shape of the substructure varied with the Hc (⊥) of the films:; no substructure was observed in the 500 Oe film, while a substructure with a needlelike shape and also a quasi-asteroid one were observed in different regions of the 1000 Oe film. The differences in the segregation conditions are strongly dependent on the Hc (⊥) of the films. Further investigation of the 1500 Oe film in the thicknees direction clearly indicated that the segregation occurs even in the initial deposition region (30 nm) and that the size of the substructure becomes larger with an increase in the film thickness.