負の一軸結晶磁気異方性をもつ軟磁性材料を用いた裏打ち膜の提案―ＷＡＴＥおよびスパイクノイズの同時抑制のために―

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Suppression of spike noise and wide adjacent track erasure (WATE) are important technical issues for perpendicular recording media (PRM) with a soft magnetic underlayer (SUL). To solve these problems simultaneously, we propose in this paper a new type of SUL with negative uniaxial perpendicular magnetic anisotropy (Ku⊥) induced by material with negative uniaxial magnetocrystalline anisotropy (Kugrain). For the proposed SUL, it can be expected that (1) WATE will be suppressed due to a wide distribution of magnetic flux under the return yoke, and that (2) spike noise will be eliminated due to the formation of a Neel wall instead of a Bloch wall. We selected hcp-CoIr as a negative kugrain material and fabricated c-plane-oriented CoIr film by sputtering. Kugrain of c-plane-oriented CoIr film had a minimum value of -6 × 106 erg/cm3 (saturation magnetization, Ms = 920 emu/cm3 ) at an Ir content of 22 at.%. In PRM using c-plane-oriented CoIr films as SULs, WATE could be suppressed compared with the PRM using amorphous CoZrNb as SUL. And from evaluation of envelopes for PRM using c-plane-oriented CoIr films as SULs, it was found that spike noise could not be clearly observed with a CoIr thickness below the calculated critical thickness of Neel wall formation.
社団法人日本磁気学会の論文