- Email: [email protected]
Ru hybrid type of underlayer for CoPtCr-SiO2 perpendicular recording media on flexible tape
ARTICLE IN PRESS Journal of Magnetism and Magnetic Materials 320 (2008) 3000–3003
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Ru-O/Ru hybrid type of underlayer for CoPtCr-SiO2 perpendicular recording media on flexible tape T. Matsuu a,, A. Hashimoto a, H. Fujiura a, S. Matsunuma b, T. Inoue b, T. Doi b, S. Nakagawa a a b
Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8577, Japan Hitachi Maxell, 6-20-1 Kinunodai , Tsukubamirai, Ibaraki 300-2496, Japan
a r t i c l e in f o
a b s t r a c t
Available online 6 August 2008
Ru/CoPtCr-SiO2 bilayer prepared at 4 and 26 mTorr of Ar gas pressure for the deposition of Ru and CoPtCr-SiO2 layers, respectively, exhibits better magnetic properties suitable for perpendicular magnetic recording media when they are deposited at room temperature on a Pt seed layer prepared at 450 1C. The Ru-O seed layer fabricated by a reactive sputtering method improves the Ru (0 0 1) texture deposited on a Ru-O layer. The Ru-O/Ru hybrid type of underlayer causes the improvement of the c-axis orientation of CoPtCr crystallites in the CoPtCr-SiO2 layer deposited on it. Fine granulation of magnetic grains in the CoPtCr-SiO2 layer is also attained when they are deposited on the Aramid type of flexible tape substrates. & 2008 Published by Elsevier B.V.
Keywords: CoPtCr-SiO2 Perpendicular magnetic recording media Ru-O/Ru hybrid type of underlayer Flexible tape
1. Introduction
2. Experimental procedure
SiO2-added CoPtCr-based alloy recording media have been widely used for perpendicular magnetic recording media to achieve higher recording density [1]. The key features of the media are fine granulation and the (0 0 1) texture of CoPtCr magnetic grains and well-isolated grain structures [2–4]. Since the (0 0 1)-textured Ru underlayer is required to attain the (0 0 1) texture of the CoPtCr magnetic grains, some seed layers, such as Pt deposited at relatively high substrate temperature, were used to attain the Ru (0 0 1) texture. Magnetic recording tape media are still much in demand to archive a huge amount of increasing information [5]. In order to produce perpendicular magnetic recording tape media for a huge archive system, it is required to fabricate CoPtCr-SiO2 films on flexible tape substrates at substrate temperatures around room temperature to avoid thermal damage to the polymer tape substrate. In this study, we introduced a RuO/Ru hybrid type of underlayer [6]. It is composed of an oxygenadded Ru bottom layer and a Ru top layer deposited on it. We found that a Ru-O seed layer promoted the (0 0 1) texture in the Ru top layer. The (0 0 1) texture in the Ru top layer enhanced the epitaxial growth of CoPtCr (0 0 1) texture. Magnetic properties and crystallographic structures of Ru-O/Ru/CoPtCr-SiO2 films were studied. Since a facing targets sputtering (FTS) system can deposit thin films at low substrate temperature without damaging the substrates, Ru-O/Ru/CoPtCr-SiO2 films were fabricated on Aramidtype polymer tape substrates by an FTS system.
Ru(48 nm)/CoPtCr-SiO2(30 nm) thin films were fabricated on SiO2/Si substrates deposited on a Pt seed layer at 450 1C using an FTS system. The background pressure was 4.0 10-6 Torr. The working Ar gas pressure for the deposition of the Ru layer (PRu) and a CoPtCr-SiO2 layer (PCoPtCr) was set at 4 and 26 mTorr, respectively. Composition of the target was Co74Pt16Cr10-SiO2(6 mol%). Ru-O/Ru/CoPtCr-SiO2 thin films were deposited directly on glass substrates or on Aramid tape substrates without any seed layers at room temperature using an FTS system. Ru-O bottom layers were prepared by a reactive sputtering method with an introduction of O2 gas into the sputtering chamber. Magnetic properties were measured using a vibrating sample magnetometer (VSM). Crystallographic and microstructures of the films were observed by X-ray diffraction (XRD) and a transmission electron microscopy (TEM).
Corresponding author. Tel.: +81 3 5734 3564; fax: +81 3 5734 2513.
E-mail address: [email protected] (T. Matsuu). 0304-8853/$ - see front matter & 2008 Published by Elsevier B.V. doi:10.1016/j.jmmm.2008.08.009
3. Result and discussion 3.1. Fabrication of Ru/CoPtCr-SiO2 thin films on a Pt seed layer Fig. 1 shows the M–H loops of Ru/CoPtCr-SiO2 thin films on a Pt seed layer for various combinations of Ar gas pressure for the deposition of Ru and CoPtCr layers, (a) PRu: 4 mTorr and PCoPtCr: 4 mTorr, (b) PRu: 4 mTorr and PCoPtCr: 26 mTorr, (c) PRu: 26 mTorr and PCoPtCr: 4 mTorr and (d) PRu: 26 mTorr and PCoPtCr: 26 mTorr. The films of (c) and (d), which were prepared at relatively high PRu
ARTICLE IN PRESS T. Matsuu et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 3000–3003
of 26 mTorr, indicate that the magnetic properties with their magnetic easy axes lie along the in-plane direction, such as longitudinal magnetic recording media. On the other hand, the films of (a) and (b) indicate that the easy axes of magnetization lie along the perpendicular direction. Especially, the (b) film prepared at PRu and PCoPtCr of 4 and 26 mTorr, respectively, exhibits high perpendicular coercivity of 2.7 kOe. The CoPtCr film prepared at high PCoPtCr of 26 mTorr reveals lower saturation magnetization than that of the film prepared at low PCoPtCr of 4 mTorr as shown in Fig. 1(b) and (d). It is well-known that sputtering at high gas pressure tends to induce fine granulation of magnetic grains with grain boundaries, and sputtering at low gas pressure tends to promote a continuous structure of morphology [7]. Consequently,
Fig. 1. M–H loops of Ru/CoPtCr-SiO2 films on a Pt seed layer (a) PRu: 4 mTorr, PCoPtCr: 4 mTorr, (b) PRu: 4 mTorr, PCoPtCr: 26 mTorr, (c) PRu: 26 mTorr, PCoPtCr: 4 mTorr and (d) PRu: 26 mTorr, PCoPtCr: 26 mTorr.
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well-isolated and fine magnetic grain structures cause the decrease of saturation magnetization because of the high PCoPtCr condition. This experiment indicates that the suitable pressures for a Ru layer and a CoPtCr-SiO2 layer were low and high Ar gas pressure, respectively, to fabricate the films suitable for perpendicular magnetic recording media.
3.2. Ru-O/Ru hybrid type of underlayer We investigated the effects of a Ru-O/Ru hybrid type of underlayer to fabricate the films suitable for perpendicular magnetic recording media deposited on polymer tape substrates without any seed layers at room temperature. Firstly, we chose glass substrates to estimate the properties of the Ru-O/Ru/CoPtCrSiO2 trilayers. Following the results mentioned above, we deposited these layers at PRu, PRu-O and PCoPtCr of 4, 4 and 26 mTorr, respectively. Figs. 2 and 3 show the M–H loops and XRD diagrams of (a) the Ru(30 nm)/CoPtCr-SiO2(30 nm) film, (b) the Ru-O(16 nm)/Ru(20 nm)/CoPtCr-SiO2(30 nm) film and (c) the Ru-O(50 nm)/CoPtCrSiO2(30 nm) film. A CoPtCr-SiO2 thin film deposited on a Ru-O/Ru underlayer possessed the perpendicular magnetization properties and CoPtCr (0 0 1) texture in XRD as shown in Fig. 3(b). Fig. 3(b) shows that a Ru layer deposited on a Ru-O layer also exhibits Ru (0 0 1) texture. Meanwhile, a CoPtCr-SiO2 film on a Ru single layer exhibits rather isotropic magnetic properties, as shown in Fig. 2(a), caused by the random orientation of the crystallites, as indicated in Fig. 3(a). A CoPtCr-SiO2 film deposited on a Ru-O single layer possessed in-plane magnetization properties, but coercivity was too small and crystallite orientation was not observed as shown in Figs. 2(c) and 3(c). These results indicate that a Ru-O/Ru hybrid type of underlayer was suitable to fabricate perpendicular magnetic recording media at room temperature without any seed layers. Neither the diffraction peaks corresponding to Ru nor that corresponding to Ru-oxide crystallites were observed in the Ru-O layers even though the oxygen partial pressure at the deposition was varied. This means that not much crystal appears in the Ru-oxide layer. Further investigation of the Ru-oxide layer is required to clarify its crystallographic microstructure and the effect on the growth mechanism of a Ru layer deposited on it. Fig. 4 shows the changes of coercivity and squareness ratio in the perpendicular and in-plane directions as a function of the oxygen partial pressure for the bottom Ru layer. Although
Fig. 2. M–H loops of (a) Ru(30 nm)/CoPtCr-SiO2(30 nm) films, (b) Ru-O(16 nm)/Ru(20 nm)/CoPtCr-SiO2(30 nm) films, and (c) Ru-O(50 nm)/CoPtCr-SiO2(30 nm) films, respectively.
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T. Matsuu et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 3000–3003
Fig. 3. XRD diagrams of (a) Ru(30 nm)/CoPtCr-SiO2(30 nm) films, (b) Ru-O(16 nm)/Ru(20 nm)/CoPtCr-SiO2(30 nm) films, and (c) Ru-O(50 nm)/CoPtCr-SiO2(30 nm) films, respectively.
Fig. 5. Ru (0 0 2) diffraction intensity as a function of oxygen partial pressure for the bottom Ru layer.
Fig. 4. The changes of coercivity and squareness ratio in the perpendicular and inplane directions as a function of the oxygen partial pressure for the bottom Ru layer.
squareness ratio in the longitudinal direction was high and coercivity was low for the oxygen partial pressure below 5%, addition of O2 above 10% caused a drastic change of the easy axis direction from the in-plane to the perpendicular direction. However, at the oxygen partial pressure of 100%, an increase of the in-plane component was observed. It implies that the optimum oxygen partial pressure exists at around 10%. Fig. 5 shows the change of the Ru (0 0 2) diffraction intensity of Ru-O/Ru films as a function of the oxygen partial pressure during the deposition of the bottom Ru-O layer. Ru (0 0 2) diffraction intensity became maximum at the oxygen partial pressure of 10%.
3.3. Ru-O/Ru/CoPtCr-SiO2 films on Aramid tape Fig. 6 shows the M–H loops of the Ru-O(16 nm)/ Ru(20 nm)/ CoPtCr-SiO2(30 nm) thin films deposited on Aramid tape substrates at room temperature at the oxygen partial pressure ratio of 10%. Coercivity and squareness ratio in the perpendicular direction were 2.6 kOe and 0.76, respectively. It indicates that perpendicular magnetic recording media can be fabricated on Aramid tape substrates.
Fig. 6. M–H loop of the Ru-O(16 nm)/Ru(20 nm)/CoPtCr- SiO2(30 nm) films deposited on Aramid tape substrates.
ARTICLE IN PRESS T. Matsuu et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 3000–3003
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miniaturization of magnetic grains were attained. Average diameter of grains was 5.9 nm.
4. Conclusion Suitable Ar gas pressure conditions for Ru and CoPtCr-SiO2 layers were 4 and 26 mTorr, respectively, to fabricate the films suitable for perpendicular magnetic recording media when Ru/CoPtCr-SiO2 films were deposited at room temperature on Pt seed layers prepared at 450 1C. A Ru-O seed layer fabricated by a reactive sputtering method using Ar and oxygen mixture gas caused the improvement of Ru (0 0 1) texture deposited on a Ru-O layer. The (0 0 1) texture of the Ru top layer causes the improvement of the c-axis orientation of CoPtCr crystallites in the CoPtCr-SiO2 layer. An appropriate oxygen partial pressure was around 10% for the deposition of a Ru-O layer. Ru-O/Ru/CoPtCrSiO2 films prepared at room temperature on Aramid tape substrates exhibited magnetization characteristics suitable for perpendicular magnetic recording media. TEM image of the film indicates fine granulation of magnetic grains with SiO2 grain boundaries. The average grain size was 5.9 nm. References
Fig. 7. TEM image and grain size distribution of Ru-O/ Ru/CoPtCr-SiO2 film deposited on Aramid tape substrate.
Fig. 7 shows a TEM image and grain size distribution of Ru-O/ Ru/CoPtCr-SiO2 films deposited on Aramid tape substrates. Fine granulation of magnetic grains with SiO2 grain boundaries and
[1] H. Uwazumi, K. Enomoto, Y. Sakai, S. Takenoiri, T. Oikawa, S. Watanabe, IEEE Trans. Magn. 39 (4) (2003) 1914. [2] T. Oikawa, M. Nakamura, H. Uwazumi, T. Shimatsu, H. Muraoka, Y. Nakamura, IEEE Trans. Magn. 38 (5) (2002) 1976. [3] H. Yamane, S. Watanabe, J. Ariake, N. Honda, K. Ouchi, S. Iwasaki, J. Magn. Magn. Mater. 30 (2005) 287. [4] T. Shimatsu, H. Sato, T. Oikawa, Y. Inaba, O. Kitakami, S. Okamoto, H. Aoi, H. Muraoka, Y. Nakamura, IEEE Trans. Magn. 40 (4) (2004) 2483. [5] H. Lee, L. Wang, J.A. Bain, D.E. Laughlin, IEEE Trans. Magn. 41 (2) (2005) 654. [6] Y. Abe, Y. Kaga, M. Kawamura, K. Sasaki, Jpn. J. Appl. Phys. 40 (12) (2001) 6956. [7] J.Z. Shi, S.N. Piramanayagam, C.S. Mah, J.M. Zhao, J. Magn. Magn. Mater. 20 (2006) 303.
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Ru-O/Ru hybrid type of underlayer for CoPtCr-SiO2 perpendicular recording media on flexible tape T. Matsuu a,, A. Hashimoto a, H. Fujiura a, S. Matsunuma b, T. Inoue b, T. Doi b, S. Nakagawa a a b
Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8577, Japan Hitachi Maxell, 6-20-1 Kinunodai , Tsukubamirai, Ibaraki 300-2496, Japan
a r t i c l e in f o
a b s t r a c t
Available online 6 August 2008
Ru/CoPtCr-SiO2 bilayer prepared at 4 and 26 mTorr of Ar gas pressure for the deposition of Ru and CoPtCr-SiO2 layers, respectively, exhibits better magnetic properties suitable for perpendicular magnetic recording media when they are deposited at room temperature on a Pt seed layer prepared at 450 1C. The Ru-O seed layer fabricated by a reactive sputtering method improves the Ru (0 0 1) texture deposited on a Ru-O layer. The Ru-O/Ru hybrid type of underlayer causes the improvement of the c-axis orientation of CoPtCr crystallites in the CoPtCr-SiO2 layer deposited on it. Fine granulation of magnetic grains in the CoPtCr-SiO2 layer is also attained when they are deposited on the Aramid type of flexible tape substrates. & 2008 Published by Elsevier B.V.
Keywords: CoPtCr-SiO2 Perpendicular magnetic recording media Ru-O/Ru hybrid type of underlayer Flexible tape
1. Introduction
2. Experimental procedure
SiO2-added CoPtCr-based alloy recording media have been widely used for perpendicular magnetic recording media to achieve higher recording density [1]. The key features of the media are fine granulation and the (0 0 1) texture of CoPtCr magnetic grains and well-isolated grain structures [2–4]. Since the (0 0 1)-textured Ru underlayer is required to attain the (0 0 1) texture of the CoPtCr magnetic grains, some seed layers, such as Pt deposited at relatively high substrate temperature, were used to attain the Ru (0 0 1) texture. Magnetic recording tape media are still much in demand to archive a huge amount of increasing information [5]. In order to produce perpendicular magnetic recording tape media for a huge archive system, it is required to fabricate CoPtCr-SiO2 films on flexible tape substrates at substrate temperatures around room temperature to avoid thermal damage to the polymer tape substrate. In this study, we introduced a RuO/Ru hybrid type of underlayer [6]. It is composed of an oxygenadded Ru bottom layer and a Ru top layer deposited on it. We found that a Ru-O seed layer promoted the (0 0 1) texture in the Ru top layer. The (0 0 1) texture in the Ru top layer enhanced the epitaxial growth of CoPtCr (0 0 1) texture. Magnetic properties and crystallographic structures of Ru-O/Ru/CoPtCr-SiO2 films were studied. Since a facing targets sputtering (FTS) system can deposit thin films at low substrate temperature without damaging the substrates, Ru-O/Ru/CoPtCr-SiO2 films were fabricated on Aramidtype polymer tape substrates by an FTS system.
Ru(48 nm)/CoPtCr-SiO2(30 nm) thin films were fabricated on SiO2/Si substrates deposited on a Pt seed layer at 450 1C using an FTS system. The background pressure was 4.0 10-6 Torr. The working Ar gas pressure for the deposition of the Ru layer (PRu) and a CoPtCr-SiO2 layer (PCoPtCr) was set at 4 and 26 mTorr, respectively. Composition of the target was Co74Pt16Cr10-SiO2(6 mol%). Ru-O/Ru/CoPtCr-SiO2 thin films were deposited directly on glass substrates or on Aramid tape substrates without any seed layers at room temperature using an FTS system. Ru-O bottom layers were prepared by a reactive sputtering method with an introduction of O2 gas into the sputtering chamber. Magnetic properties were measured using a vibrating sample magnetometer (VSM). Crystallographic and microstructures of the films were observed by X-ray diffraction (XRD) and a transmission electron microscopy (TEM).
Corresponding author. Tel.: +81 3 5734 3564; fax: +81 3 5734 2513.
E-mail address: [email protected] (T. Matsuu). 0304-8853/$ - see front matter & 2008 Published by Elsevier B.V. doi:10.1016/j.jmmm.2008.08.009
3. Result and discussion 3.1. Fabrication of Ru/CoPtCr-SiO2 thin films on a Pt seed layer Fig. 1 shows the M–H loops of Ru/CoPtCr-SiO2 thin films on a Pt seed layer for various combinations of Ar gas pressure for the deposition of Ru and CoPtCr layers, (a) PRu: 4 mTorr and PCoPtCr: 4 mTorr, (b) PRu: 4 mTorr and PCoPtCr: 26 mTorr, (c) PRu: 26 mTorr and PCoPtCr: 4 mTorr and (d) PRu: 26 mTorr and PCoPtCr: 26 mTorr. The films of (c) and (d), which were prepared at relatively high PRu
ARTICLE IN PRESS T. Matsuu et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 3000–3003
of 26 mTorr, indicate that the magnetic properties with their magnetic easy axes lie along the in-plane direction, such as longitudinal magnetic recording media. On the other hand, the films of (a) and (b) indicate that the easy axes of magnetization lie along the perpendicular direction. Especially, the (b) film prepared at PRu and PCoPtCr of 4 and 26 mTorr, respectively, exhibits high perpendicular coercivity of 2.7 kOe. The CoPtCr film prepared at high PCoPtCr of 26 mTorr reveals lower saturation magnetization than that of the film prepared at low PCoPtCr of 4 mTorr as shown in Fig. 1(b) and (d). It is well-known that sputtering at high gas pressure tends to induce fine granulation of magnetic grains with grain boundaries, and sputtering at low gas pressure tends to promote a continuous structure of morphology [7]. Consequently,
Fig. 1. M–H loops of Ru/CoPtCr-SiO2 films on a Pt seed layer (a) PRu: 4 mTorr, PCoPtCr: 4 mTorr, (b) PRu: 4 mTorr, PCoPtCr: 26 mTorr, (c) PRu: 26 mTorr, PCoPtCr: 4 mTorr and (d) PRu: 26 mTorr, PCoPtCr: 26 mTorr.
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well-isolated and fine magnetic grain structures cause the decrease of saturation magnetization because of the high PCoPtCr condition. This experiment indicates that the suitable pressures for a Ru layer and a CoPtCr-SiO2 layer were low and high Ar gas pressure, respectively, to fabricate the films suitable for perpendicular magnetic recording media.
3.2. Ru-O/Ru hybrid type of underlayer We investigated the effects of a Ru-O/Ru hybrid type of underlayer to fabricate the films suitable for perpendicular magnetic recording media deposited on polymer tape substrates without any seed layers at room temperature. Firstly, we chose glass substrates to estimate the properties of the Ru-O/Ru/CoPtCrSiO2 trilayers. Following the results mentioned above, we deposited these layers at PRu, PRu-O and PCoPtCr of 4, 4 and 26 mTorr, respectively. Figs. 2 and 3 show the M–H loops and XRD diagrams of (a) the Ru(30 nm)/CoPtCr-SiO2(30 nm) film, (b) the Ru-O(16 nm)/Ru(20 nm)/CoPtCr-SiO2(30 nm) film and (c) the Ru-O(50 nm)/CoPtCrSiO2(30 nm) film. A CoPtCr-SiO2 thin film deposited on a Ru-O/Ru underlayer possessed the perpendicular magnetization properties and CoPtCr (0 0 1) texture in XRD as shown in Fig. 3(b). Fig. 3(b) shows that a Ru layer deposited on a Ru-O layer also exhibits Ru (0 0 1) texture. Meanwhile, a CoPtCr-SiO2 film on a Ru single layer exhibits rather isotropic magnetic properties, as shown in Fig. 2(a), caused by the random orientation of the crystallites, as indicated in Fig. 3(a). A CoPtCr-SiO2 film deposited on a Ru-O single layer possessed in-plane magnetization properties, but coercivity was too small and crystallite orientation was not observed as shown in Figs. 2(c) and 3(c). These results indicate that a Ru-O/Ru hybrid type of underlayer was suitable to fabricate perpendicular magnetic recording media at room temperature without any seed layers. Neither the diffraction peaks corresponding to Ru nor that corresponding to Ru-oxide crystallites were observed in the Ru-O layers even though the oxygen partial pressure at the deposition was varied. This means that not much crystal appears in the Ru-oxide layer. Further investigation of the Ru-oxide layer is required to clarify its crystallographic microstructure and the effect on the growth mechanism of a Ru layer deposited on it. Fig. 4 shows the changes of coercivity and squareness ratio in the perpendicular and in-plane directions as a function of the oxygen partial pressure for the bottom Ru layer. Although
Fig. 2. M–H loops of (a) Ru(30 nm)/CoPtCr-SiO2(30 nm) films, (b) Ru-O(16 nm)/Ru(20 nm)/CoPtCr-SiO2(30 nm) films, and (c) Ru-O(50 nm)/CoPtCr-SiO2(30 nm) films, respectively.
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Fig. 3. XRD diagrams of (a) Ru(30 nm)/CoPtCr-SiO2(30 nm) films, (b) Ru-O(16 nm)/Ru(20 nm)/CoPtCr-SiO2(30 nm) films, and (c) Ru-O(50 nm)/CoPtCr-SiO2(30 nm) films, respectively.
Fig. 5. Ru (0 0 2) diffraction intensity as a function of oxygen partial pressure for the bottom Ru layer.
Fig. 4. The changes of coercivity and squareness ratio in the perpendicular and inplane directions as a function of the oxygen partial pressure for the bottom Ru layer.
squareness ratio in the longitudinal direction was high and coercivity was low for the oxygen partial pressure below 5%, addition of O2 above 10% caused a drastic change of the easy axis direction from the in-plane to the perpendicular direction. However, at the oxygen partial pressure of 100%, an increase of the in-plane component was observed. It implies that the optimum oxygen partial pressure exists at around 10%. Fig. 5 shows the change of the Ru (0 0 2) diffraction intensity of Ru-O/Ru films as a function of the oxygen partial pressure during the deposition of the bottom Ru-O layer. Ru (0 0 2) diffraction intensity became maximum at the oxygen partial pressure of 10%.
3.3. Ru-O/Ru/CoPtCr-SiO2 films on Aramid tape Fig. 6 shows the M–H loops of the Ru-O(16 nm)/ Ru(20 nm)/ CoPtCr-SiO2(30 nm) thin films deposited on Aramid tape substrates at room temperature at the oxygen partial pressure ratio of 10%. Coercivity and squareness ratio in the perpendicular direction were 2.6 kOe and 0.76, respectively. It indicates that perpendicular magnetic recording media can be fabricated on Aramid tape substrates.
Fig. 6. M–H loop of the Ru-O(16 nm)/Ru(20 nm)/CoPtCr- SiO2(30 nm) films deposited on Aramid tape substrates.
ARTICLE IN PRESS T. Matsuu et al. / Journal of Magnetism and Magnetic Materials 320 (2008) 3000–3003
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miniaturization of magnetic grains were attained. Average diameter of grains was 5.9 nm.
4. Conclusion Suitable Ar gas pressure conditions for Ru and CoPtCr-SiO2 layers were 4 and 26 mTorr, respectively, to fabricate the films suitable for perpendicular magnetic recording media when Ru/CoPtCr-SiO2 films were deposited at room temperature on Pt seed layers prepared at 450 1C. A Ru-O seed layer fabricated by a reactive sputtering method using Ar and oxygen mixture gas caused the improvement of Ru (0 0 1) texture deposited on a Ru-O layer. The (0 0 1) texture of the Ru top layer causes the improvement of the c-axis orientation of CoPtCr crystallites in the CoPtCr-SiO2 layer. An appropriate oxygen partial pressure was around 10% for the deposition of a Ru-O layer. Ru-O/Ru/CoPtCrSiO2 films prepared at room temperature on Aramid tape substrates exhibited magnetization characteristics suitable for perpendicular magnetic recording media. TEM image of the film indicates fine granulation of magnetic grains with SiO2 grain boundaries. The average grain size was 5.9 nm. References
Fig. 7. TEM image and grain size distribution of Ru-O/ Ru/CoPtCr-SiO2 film deposited on Aramid tape substrate.
Fig. 7 shows a TEM image and grain size distribution of Ru-O/ Ru/CoPtCr-SiO2 films deposited on Aramid tape substrates. Fine granulation of magnetic grains with SiO2 grain boundaries and
[1] H. Uwazumi, K. Enomoto, Y. Sakai, S. Takenoiri, T. Oikawa, S. Watanabe, IEEE Trans. Magn. 39 (4) (2003) 1914. [2] T. Oikawa, M. Nakamura, H. Uwazumi, T. Shimatsu, H. Muraoka, Y. Nakamura, IEEE Trans. Magn. 38 (5) (2002) 1976. [3] H. Yamane, S. Watanabe, J. Ariake, N. Honda, K. Ouchi, S. Iwasaki, J. Magn. Magn. Mater. 30 (2005) 287. [4] T. Shimatsu, H. Sato, T. Oikawa, Y. Inaba, O. Kitakami, S. Okamoto, H. Aoi, H. Muraoka, Y. Nakamura, IEEE Trans. Magn. 40 (4) (2004) 2483. [5] H. Lee, L. Wang, J.A. Bain, D.E. Laughlin, IEEE Trans. Magn. 41 (2) (2005) 654. [6] Y. Abe, Y. Kaga, M. Kawamura, K. Sasaki, Jpn. J. Appl. Phys. 40 (12) (2001) 6956. [7] J.Z. Shi, S.N. Piramanayagam, C.S. Mah, J.M. Zhao, J. Magn. Magn. Mater. 20 (2006) 303.