THERMALLY STABLE ULTRA HIGH DENSITY THIN FILM MAGNETIC MEDIA

All the thin film media used in this study were prepared with an in-line thin film deposition machine，which has6separated chambers for sputtering.The ultimate vacuum pressure for each chamber was better than 3×10 I D1-9 I D 1 Torr.To remove impurities from the substrate surface，prior to film deposition，dry-etching was performed by rf sputtering。The compositions of magnetic layer were CoCrPt，CoCrTaPt and CoCrPtB.The Cr，Pt，Ta B content was widely varied。The results get from the evaluation of magnetic properties，microstructure and read-write properties are written below.1。The intergranular magnetic coupling and the grain size in CoCrPt media with B addition are both reduced.On the other hand，the substitution of Cr with Ta in CoCrPt media increases the grain size。The read-write evaluation shows that the addition of B into CoCrPt reduces the media noise significantly.However，the media noise of CoCrTaPt media is lower compared with CoCrPtB，though the CoCrTaPt media has larger grain size compared with CoCrPtB media.This is due the relatively lower intergranular exchange coupling in CoCrTaPt media，compared with CoCrPtB media。From this result，we can conclude that the addition of both Ta and B into CoCrPt media is effective to reduce the media noise.2。To realize a media which is thermally stable，the thermal stability factor v i D2 act文件D 2 K文件D 2 u文件D 2 I D 1 grain文件D1/kT must be larger than 85.It is concluded that to realize low noise media which is thermally stable，the coercivity H I D 2 c e D2，the anisotropy field H I D 2 k D 2 D 2 D 1 grain D 1 and the magnetocrystalline anisotropy y energy K 2 u D 2.With the assumption that the saturation magnetization is M I D2s I D2=300emu/cm I D13文件D1，the squareness S=0.7，remanence magnetization M I D 1 r文件D1=210 emu/cm I D 13文件D1，film thickness t I D 2 mag文件D2=15 nm，v I D 2 act文件D 2 K I D 2 u文件D2/kT=85，magnetic cluster GD D 2 act D 2=12 nm.

All the thin film media used in this study were prepared with an in-line thin film deposition machine, which has 6 separated chambers for sputtering. The ultimate vacuum pressure for each chamber was better than 3×10ィイD1-9ィエD1 Torr. To remove impurities from the substrate surface, prior to film deposition, dry-etching was performed by rf sputtering. The compositions of magnetic layer were CoCrPt, CoCrTaPt and CoCrPtB. The Cr, Pt, Ta B content was widely varied. The results get from the evaluation of magnetic properties, microstructure and read-write properties are written below.1. The intergranular magnetic coupling and the grain size in CoCrPt media with B addition are both reduced. On the other hand, the substitution of Cr with Ta in CoCrPt media increases the grain size. The read-write evaluation shows that the addition of B into CoCrPt reduces the media noise significantly. However, the media noise of CoCrTaPt media is lower compared with CoCrPtB, though the CoCrTaPt media has larger grain size compared with CoCrPtB media. This is due the relatively lower intergranular exchange coupling in CoCrTaPt media, compared with CoCrPtB media. From this result, we can conclude that the addition of both Ta and B into CoCrPt media is effective to reduce the media noise.2. To realize a media which is thermally stable, the thermal stability factor vィイD2actィエD2KィイD2uィエD2ィイD1grainィエD1/kT must be larger than 85.It is concluded that to realize low noise media which is thermally stable, the coercivity HィイD2cィエD2, the anisotropy field HィイD2kィエD2ィイD1grainィエD1 and the magnetocrystalline anisotropy energy KィイD2uィエD2ィイD1grainィエD1 should be 5 kOe, 14 kOe and 2.1×10ィイD16ィエD1 erg/cmィイD13ィエD1, respectively. With the assumption that the saturation magnetization is MィイD2sィエD2=300 emu/cmィイD13ィエD1, the squareness S=0.7, remanence magnetization MィイD1rィエD1=210 emu/cmィイD13ィエD1, film thickness tィイD2magィエD2=15 nm, vィイD2actィエD2KィイD2uィエD2ィイD1grainィエD1/kT=85, magnetic cluster GDィイD2actィエD2=12 nm.