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Ag(Cu) nanocomposite films for ultra-high density perpendicular magnetic recording media
Thin Solid Films 505 (2006) 77 – 80 www.elsevier.com/locate/tsf
CoPt/Ag(Cu) nanocomposite films for ultra-high density perpendicular magnetic recording media Hao Wang a,*, S.X. Xue a, F.J. Yang a, H.B. Wang a, X. Cao a, J.A. Wang a, Y. Gao a, Z.B. Huang a, C.P. Yang a, W.Y. Cheung b, S.P. Wong b, Q. Li c, Z.Y. Li d a
Faculty of Physics and Electronic Technology and Nanotechnology Research Centre, Hubei University, Wuhan 430062, PR China b Department of Electronic Engineering, The Chinese University of Hong Kong, Hong Kong c Department of Physics, The Chinese University of Hong Kong, Hong Kong d Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, PR China Available online 15 November 2005
Abstract CoPt/Ag nanocomposite films have been prepared by magnetron sputtering and subsequent annealing. The effect of Ag on the structure and magnetic properties of CoPt/Ag nanocomposite films was investigated. It was found that the existence of the Ag plays a dominant role in inducing the (001) texture of the film. (001) textured CoPt/Ag nanocomposite films with a large perpendicular coercivity in the range of 5.6 – 7.0 kOe have been achieved after annealing at 600 -C. The Cu additive is very effective to reduce the ordering temperature in CoPtAg system. With Cu additive, the CoPtCuAg films start ordering at a lower annealing temperature of 450 -C, which is lower by 150 -C than the pure CoPtAg films. D 2005 Published by Elsevier B.V. PACS: 75.30.Gw; 75.50.Kj; 75.70.Ak Keywords: CoPt; Nanocomposite; Ordering; Magnetic recording
1. Introduction Sputtered nanocomposite films consisting of CoPt (or FePt) particles, with the high magnetic anisotropy L10 structure have attracted increasing attentions due to their possible application as ultrahigh density perpendicular magnetic recording media [1 –4]. For perpendicular magnetic recording media, it is very important to control the crystallographic orientation so that the magnetic easy axis can along the film normal. A disadvantage of the sputter deposited nanocomposite films is their tendency to grow with a (111) texture thus having the easy-magnetization direction (001) at an angle of 36- above the film plane. Recently, (001) texture has been achieved by annealing CoPt/Ag bilayers [2,5] and FePt/B2O3 nanocomposite films [6]. Karanasos et al. found that CoPt/Ag nanocomposite films with a thickness below 15 nm consist of (001) textured islands. While as the thickness increase, the islands coalesce into a continuous film * Corresponding author. Tel: +86 27 88662550; fax: +86 27 88662550. E-mail addresses: [email protected], [email protected] (H. Wang). 0040-6090/$ - see front matter D 2005 Published by Elsevier B.V. doi:10.1016/j.tsf.2005.10.007
and the (001) texture disappears. In the case of the film thickness of 12 nm, a well (001) textured CoPt/Ag nanocomposite film with a perpendicular coercivity of 4.2 kOe was obtained [2]. In general, an annealing temperature above 600 -C is necessary to obtain the L10-ordered structure for CoPtAg system. From a practical view of point, such a high temperature process is unsuitable for mass production of magnetic recording media. Hence, there have been many attempts to reduce the ordering temperature. The addition of a third element, such as Sn, Pb, Sb, Bi, B, Cu, into CoPt was reported to be effective for reducing the ordering temperature [7– 10]. However, little work is related to the reducing of ordering temperature in CoP- and FePt-based films in the case of perpendicular recording media application. In this study, we have prepared (001)-textured CoPt/Ag nanocomposite films by directly sputtering films on oxidized (100) Si substrates and subsequent annealing. In addition, on the basis of the (001) textured CoPtAg films, we added little (about 5 at.%) Cu into to the CoPtAg films and investigated the effect of Cu additive on L10 phase ordering temperature of CoPtAg nanocomposite films.
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H. Wang et al. / Thin Solid Films 505 (2006) 77 – 80
800
2. Experimental procedure
Co35Pt38Ag27 Co37Pt39Ag24 Co38Pt42Ag20 Co40Pt43Ag17
600 400
M (emu/cm3)
The (CoPt/Ag)3 multilayers precursor with Ag as the first layer in every unit were deposited by DC magnetron sputtering at ambient temperature onto (100) Si substrates covered with a 80 nm SiO2 layer. The CoPt layer was deposited by cosputtering with Pt chips equably placed on the Co target. In the case of CoPtCuAg film, (CoPt/Cu/Ag)3 precursor was used alternatively. The as-deposited films were annealed in a vacuum (¨ 10 4 Pa) at various temperatures. X-ray diffraction (XRD) spectra were collected with a Bruker D8 powder diffractometer using Cu-K a radiation. The magnetic properties of the films were examined by a vibrating sample magnetometer (VSM). The composition and thickness of the films were estimated by Rutherford Backscattering Spectrometry (RBS) using a 2 MV tandem accelerator.
200
out of plane
0 -200 -400 -600 -800 -2
-1
0
1
2
Applied Field (T) Fig. 2. The room temperature perpendicular magnetic hysteresis loops of the CoPtAg films with different Ag content after annealing at 600 -C.
3. Results and discussion
Co37Pt39Ag24
100
Co38Pt42Ag20
50 Co40Pt43Ag17
0
150 120
CoPtCu(002)
CoPtCu(001)
Co35Pt38Ag27
CoPtCu(111)
CoPt(002)
Ag(200)
180
200 150
talline CoPt with randomly oriented grains [11]. This indicates that the existence of the Ag plays a dominant role in inducing the (001) texture of the film. The mechanism how Ag induce the (001) texture of the film is not clear. One possibility is that Ag in the film tends to orientate and then induce the orientation of CoPt during annealing. RBS results have shown that some Ag atoms tend to diffuse to the surface or the film/substrate interface to form a thin top or under layer after annealing. As shown in XRD patterns in Fig. 1, with the increasing of Ag content, Ag(200) peak became more and more clear compared to other peaks, suggesting the tendency of (200) preferred orientation of the Ag top or under layer. On the other hand, L10 CoPt phase is face centered tetragonal with a > c, with the Ag(200) preferred top or under layer, the c axis of the L10 CoPt phase tend to along the film normal during the transition from fcc to fct, so that the a axis can match better with (200) orientation preferred Ag holding larger lattice parameter. Then, the mismatch between CoPt and Ag can be smaller. Similar results were reported in FePt/Ag system [12].
Intensity (a.u.)
Intensity (a.u.)
250
Ag(111)
300
CoPt(111)
CoPt(001)
A series of sample with Ag atomic content between 17% and 27% were prepared in order to study the effect of Ag content on the magnetic properties of the CoPtAg films. Typical XRD patterns of four selected samples annealed at 600 -C for 10 min are presented in Fig. 1. After annealing at 600 -C, the (001) supperlattice peak can be observed in all four samples, indicating the formation of the ordered L10 facecentered-tetragonal (fct) CoPt phase. In addition, a high ratio of the (001) peak intensity to that of (111) peak suggests that a (001) preferred orientation is obtained after annealing at 600 -C. The value of I(001)/I(111) ratio is an indication of texture, the larger the ratio the better the (001) texture. As shown in Fig. 1, with the increasing of the Ag content, a tendency of the value of I(001)/I(111) increases gradually. In the case of Co35Pt38Ag27 film with the largest Ag content, apart from the fct-CoPt (001) and (002) reflections, only a weak (111) reflection was observed, the I(001)/I(111) ratio is about 10, which is much larger than the value of 0.36 for a polycrys-
550oC
90 60
500oC
30
450oC 400oC
0 20
30
40
50
60
2θ (deg) Fig. 1. XRD patterns of the CoPtAg films with different Ag content after annealing at 600 -C.
20
30
40
50
60
2θ θ (deg) Fig. 3. XRD patterns of the Co32Pt35Cu5Ag28 film after annealing at different temperature.
H. Wang et al. / Thin Solid Films 505 (2006) 77 – 80
600
out-of-plane in-plane
Intensity (a.u.)
400 200 0 -200 -400 -600 -15
-10
-5
0
5
10
15
79
I(001)/I(111) ratio is small for the sample after annealing at 450 -C and increases significantly for the sample after annealing at the temperature above 500 -C, indicating the enhancement of (001) texture after annealing at appropriate high temperature. Typical magnetic hysteresis loops for a 25 nm Co32Pt35Cu5Ag28 film annealed at 500 -C for 30 min, with applied field in directions both perpendicular and parallel to the film, are shown in Fig. 4. The magnetic hysteresis loops show a coercivity of 7.2 kOe out of plane and a coercivity of 4.8 kOe in plane, indicating the film orientation is perpendicular preferred. These are consistent with XRD results.
Applied Field (kOe) Fig. 4. The room temperature magnetic hysteresis loops of the Co32Pt35Cu5Ag28 film after annealing at 500 -C for 30 min.
The magnetic properties for the CoPtAg films were measured with the applied field perpendicular to the film plane at room temperature. In Fig. 2, the perpendicular magnetic hysteresis loops of four typical CoPtAg samples with different Ag content annealed at 600 -C are presented. It can be seen that all loops show a large perpendicular coercivity in the range of 5.6 –7.0 kOe with the magnetization about 600 emu/cm3, which indicate a high ordering transformation into the fct structure and a well (001) texture have been achieved in the post-annealed films. The coercivity gradually increases with the decreasing of Ag concentration, which is related to the enhancement of CoPt grain size in the composite film. Ag addition generally suppresses the CoPt grain growth during annealing, the less Ag content, the larger CoPt grain size. Especially, the Co40Pt43Ag17 film with the highest Ag concentration after annealing at 600 -C exhibits the largest perpendicular coercivity of 7.0 kOe, a high magnetization of 650 emu/cm3 and a squareness of 0.95. In general, an annealing process above 600 -C is necessary to obtain the L10-ordered structure in CoPtAg system. Such high-temperature treatments are undesirable for the manufacturing process. Previous study indicated that Cu addition is very effective to reduce the ordering temperature of L10-CoPt. The possible mechanism is that smaller Cu atoms diffuse into the CoPt crystal lattice, as a result, the crystal lattice has a small change owing to the formation of CoPtCu alloys. Thus, the activation energy for the disorder/ order transformation would be lowered. Can the Cu addition also help to reduce the ordering temperature of the above mentioned CoPtAg films but still keeping the (001) texture? To find the answer, we insert a very thin Cu layer between CoPt and Ag in every unit while depositing the multilayer precursors, leading to a little content (about 5% in atomic ratio) of Cu in the whole nanocomposite film after annealing. Shown in Fig. 3 are the XRD patterns of the Co32Pt35Cu5Ag28 film annealed at various temperatures for 30 min. With Cu additive, the CoPtAg film starts ordering at a lower annealing temperature of 450 -C, which is lower by 150 -C than the pure CoPtAg films. On the other hand, the
4. Conclusions CoPt/Ag nanocomposite films have been prepared by magnetron sputtering and subsequent annealing. The effect of Ag on the structure and magnetic properties of CoPt/Ag nanocomposite films was investigated. It was found that the existence of the Ag plays a dominant role in inducing the (001) texture of the film. (001) texture and a large perpendicular coercivity in the range of 5.6 –7.0 kOe have been achieved in the CoPtAg films after annealing at 600 -C. The Cu additive is very effective to reduce the ordering temperature in CoPtAg system. With little Cu additive, the CoPtAg films start ordering at a lower annealing temperature of 450 -C, which is lower by 150 -C than the pure CoPtAg films. A perpendicular orientation preferred Co32Pt35Cu5Ag28 nanocomposite film, with a low ordering temperature of 500 -C and a large perpendicular coercivity of 7.2 kOe, has been achieved successfully. Acknowledgements This work is supported in part by the National Nature Science Foundation of China under Grant No.50371056 and 60490291, Outstanding Yong Scientist Foundation of Hubei Province (2005ABB033), Excellent Creative Research Team Project of Hubei Province and Hubei University, Key project of Educational Department of Hubei Province (2004Z003), and the Research Grants Council of Hong Kong SAR (Ref. No. CUHK4182/04E). References [1] C. Chen, R. Sakurai, M. Hashimoto, J. Shi, Y. Nakamura, Thin Solid Films 459 (2004) 200. [2] V. Karanasos, I. Panagiotopoulos, D. Niarchos, J. Magn. Magn. Mater. 249 (2002) 471. [3] S. Stavroyiannis, I. Panagiotopoulos, D. Niarchos, J.A. Christodoulides, Y. Zhang, G.C. Hadjipanayis, Appl. Phys. Lett. 73 (1998) 3453. [4] H. Wang, S.P. Wong, W.Y. Cheung, N. Ke, M.F. Chiah, H. Liu, X.X. Zhang, J. Appl. Phys. 88 (2000) 2063. [5] V. Karanasos, I. Panagiotopoulos, D. Niarchos, Appl. Phys. Lett. 79 (2001) 1255. [6] C.P. Luo, S.H. Liou, L. Gao, Y. Liu, D.J. Sellmyer, Appl. Phys. Lett. 77 (2000) 2225.
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[7] C. Chen, O. Kitakami, S. Okamoto, Y. Shimada, Appl. Phys. Lett. 76 (2000) 3218. [8] H. Yamaguchi, O. Kitakami, S. Okamoto, Y. Shimada, K. Oikawa, K. Fukamichi, Appl. Phys. Lett. 79 (2001) 2001. [9] O. Kitakami, Y. Shimada, K. Oikawa, H. Daimon, K. Fukamichi, Appl. Phys. Lett. 78 (2001) 1104.
[10] T. Maeda, T. Kai, A. Kikitsu, T. Nagase, J. Akiyama, Appl. Phys. Lett. 80 (2002) 2147. [11] W.M. Liao, Y.P. Lin, F.T. Yuan, S.K. Chen, J. Magn. Magn. Mater. 272 (2004) 2175. [12] Y.N. Hsu, S. Jeong, D.E. Laughlin, J. Appl. Phys. 89 (2001) 7068.
CoPt/Ag(Cu) nanocomposite films for ultra-high density perpendicular magnetic recording media Hao Wang a,*, S.X. Xue a, F.J. Yang a, H.B. Wang a, X. Cao a, J.A. Wang a, Y. Gao a, Z.B. Huang a, C.P. Yang a, W.Y. Cheung b, S.P. Wong b, Q. Li c, Z.Y. Li d a
Faculty of Physics and Electronic Technology and Nanotechnology Research Centre, Hubei University, Wuhan 430062, PR China b Department of Electronic Engineering, The Chinese University of Hong Kong, Hong Kong c Department of Physics, The Chinese University of Hong Kong, Hong Kong d Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, PR China Available online 15 November 2005
Abstract CoPt/Ag nanocomposite films have been prepared by magnetron sputtering and subsequent annealing. The effect of Ag on the structure and magnetic properties of CoPt/Ag nanocomposite films was investigated. It was found that the existence of the Ag plays a dominant role in inducing the (001) texture of the film. (001) textured CoPt/Ag nanocomposite films with a large perpendicular coercivity in the range of 5.6 – 7.0 kOe have been achieved after annealing at 600 -C. The Cu additive is very effective to reduce the ordering temperature in CoPtAg system. With Cu additive, the CoPtCuAg films start ordering at a lower annealing temperature of 450 -C, which is lower by 150 -C than the pure CoPtAg films. D 2005 Published by Elsevier B.V. PACS: 75.30.Gw; 75.50.Kj; 75.70.Ak Keywords: CoPt; Nanocomposite; Ordering; Magnetic recording
1. Introduction Sputtered nanocomposite films consisting of CoPt (or FePt) particles, with the high magnetic anisotropy L10 structure have attracted increasing attentions due to their possible application as ultrahigh density perpendicular magnetic recording media [1 –4]. For perpendicular magnetic recording media, it is very important to control the crystallographic orientation so that the magnetic easy axis can along the film normal. A disadvantage of the sputter deposited nanocomposite films is their tendency to grow with a (111) texture thus having the easy-magnetization direction (001) at an angle of 36- above the film plane. Recently, (001) texture has been achieved by annealing CoPt/Ag bilayers [2,5] and FePt/B2O3 nanocomposite films [6]. Karanasos et al. found that CoPt/Ag nanocomposite films with a thickness below 15 nm consist of (001) textured islands. While as the thickness increase, the islands coalesce into a continuous film * Corresponding author. Tel: +86 27 88662550; fax: +86 27 88662550. E-mail addresses: [email protected], [email protected] (H. Wang). 0040-6090/$ - see front matter D 2005 Published by Elsevier B.V. doi:10.1016/j.tsf.2005.10.007
and the (001) texture disappears. In the case of the film thickness of 12 nm, a well (001) textured CoPt/Ag nanocomposite film with a perpendicular coercivity of 4.2 kOe was obtained [2]. In general, an annealing temperature above 600 -C is necessary to obtain the L10-ordered structure for CoPtAg system. From a practical view of point, such a high temperature process is unsuitable for mass production of magnetic recording media. Hence, there have been many attempts to reduce the ordering temperature. The addition of a third element, such as Sn, Pb, Sb, Bi, B, Cu, into CoPt was reported to be effective for reducing the ordering temperature [7– 10]. However, little work is related to the reducing of ordering temperature in CoP- and FePt-based films in the case of perpendicular recording media application. In this study, we have prepared (001)-textured CoPt/Ag nanocomposite films by directly sputtering films on oxidized (100) Si substrates and subsequent annealing. In addition, on the basis of the (001) textured CoPtAg films, we added little (about 5 at.%) Cu into to the CoPtAg films and investigated the effect of Cu additive on L10 phase ordering temperature of CoPtAg nanocomposite films.
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H. Wang et al. / Thin Solid Films 505 (2006) 77 – 80
800
2. Experimental procedure
Co35Pt38Ag27 Co37Pt39Ag24 Co38Pt42Ag20 Co40Pt43Ag17
600 400
M (emu/cm3)
The (CoPt/Ag)3 multilayers precursor with Ag as the first layer in every unit were deposited by DC magnetron sputtering at ambient temperature onto (100) Si substrates covered with a 80 nm SiO2 layer. The CoPt layer was deposited by cosputtering with Pt chips equably placed on the Co target. In the case of CoPtCuAg film, (CoPt/Cu/Ag)3 precursor was used alternatively. The as-deposited films were annealed in a vacuum (¨ 10 4 Pa) at various temperatures. X-ray diffraction (XRD) spectra were collected with a Bruker D8 powder diffractometer using Cu-K a radiation. The magnetic properties of the films were examined by a vibrating sample magnetometer (VSM). The composition and thickness of the films were estimated by Rutherford Backscattering Spectrometry (RBS) using a 2 MV tandem accelerator.
200
out of plane
0 -200 -400 -600 -800 -2
-1
0
1
2
Applied Field (T) Fig. 2. The room temperature perpendicular magnetic hysteresis loops of the CoPtAg films with different Ag content after annealing at 600 -C.
3. Results and discussion
Co37Pt39Ag24
100
Co38Pt42Ag20
50 Co40Pt43Ag17
0
150 120
CoPtCu(002)
CoPtCu(001)
Co35Pt38Ag27
CoPtCu(111)
CoPt(002)
Ag(200)
180
200 150
talline CoPt with randomly oriented grains [11]. This indicates that the existence of the Ag plays a dominant role in inducing the (001) texture of the film. The mechanism how Ag induce the (001) texture of the film is not clear. One possibility is that Ag in the film tends to orientate and then induce the orientation of CoPt during annealing. RBS results have shown that some Ag atoms tend to diffuse to the surface or the film/substrate interface to form a thin top or under layer after annealing. As shown in XRD patterns in Fig. 1, with the increasing of Ag content, Ag(200) peak became more and more clear compared to other peaks, suggesting the tendency of (200) preferred orientation of the Ag top or under layer. On the other hand, L10 CoPt phase is face centered tetragonal with a > c, with the Ag(200) preferred top or under layer, the c axis of the L10 CoPt phase tend to along the film normal during the transition from fcc to fct, so that the a axis can match better with (200) orientation preferred Ag holding larger lattice parameter. Then, the mismatch between CoPt and Ag can be smaller. Similar results were reported in FePt/Ag system [12].
Intensity (a.u.)
Intensity (a.u.)
250
Ag(111)
300
CoPt(111)
CoPt(001)
A series of sample with Ag atomic content between 17% and 27% were prepared in order to study the effect of Ag content on the magnetic properties of the CoPtAg films. Typical XRD patterns of four selected samples annealed at 600 -C for 10 min are presented in Fig. 1. After annealing at 600 -C, the (001) supperlattice peak can be observed in all four samples, indicating the formation of the ordered L10 facecentered-tetragonal (fct) CoPt phase. In addition, a high ratio of the (001) peak intensity to that of (111) peak suggests that a (001) preferred orientation is obtained after annealing at 600 -C. The value of I(001)/I(111) ratio is an indication of texture, the larger the ratio the better the (001) texture. As shown in Fig. 1, with the increasing of the Ag content, a tendency of the value of I(001)/I(111) increases gradually. In the case of Co35Pt38Ag27 film with the largest Ag content, apart from the fct-CoPt (001) and (002) reflections, only a weak (111) reflection was observed, the I(001)/I(111) ratio is about 10, which is much larger than the value of 0.36 for a polycrys-
550oC
90 60
500oC
30
450oC 400oC
0 20
30
40
50
60
2θ (deg) Fig. 1. XRD patterns of the CoPtAg films with different Ag content after annealing at 600 -C.
20
30
40
50
60
2θ θ (deg) Fig. 3. XRD patterns of the Co32Pt35Cu5Ag28 film after annealing at different temperature.
H. Wang et al. / Thin Solid Films 505 (2006) 77 – 80
600
out-of-plane in-plane
Intensity (a.u.)
400 200 0 -200 -400 -600 -15
-10
-5
0
5
10
15
79
I(001)/I(111) ratio is small for the sample after annealing at 450 -C and increases significantly for the sample after annealing at the temperature above 500 -C, indicating the enhancement of (001) texture after annealing at appropriate high temperature. Typical magnetic hysteresis loops for a 25 nm Co32Pt35Cu5Ag28 film annealed at 500 -C for 30 min, with applied field in directions both perpendicular and parallel to the film, are shown in Fig. 4. The magnetic hysteresis loops show a coercivity of 7.2 kOe out of plane and a coercivity of 4.8 kOe in plane, indicating the film orientation is perpendicular preferred. These are consistent with XRD results.
Applied Field (kOe) Fig. 4. The room temperature magnetic hysteresis loops of the Co32Pt35Cu5Ag28 film after annealing at 500 -C for 30 min.
The magnetic properties for the CoPtAg films were measured with the applied field perpendicular to the film plane at room temperature. In Fig. 2, the perpendicular magnetic hysteresis loops of four typical CoPtAg samples with different Ag content annealed at 600 -C are presented. It can be seen that all loops show a large perpendicular coercivity in the range of 5.6 –7.0 kOe with the magnetization about 600 emu/cm3, which indicate a high ordering transformation into the fct structure and a well (001) texture have been achieved in the post-annealed films. The coercivity gradually increases with the decreasing of Ag concentration, which is related to the enhancement of CoPt grain size in the composite film. Ag addition generally suppresses the CoPt grain growth during annealing, the less Ag content, the larger CoPt grain size. Especially, the Co40Pt43Ag17 film with the highest Ag concentration after annealing at 600 -C exhibits the largest perpendicular coercivity of 7.0 kOe, a high magnetization of 650 emu/cm3 and a squareness of 0.95. In general, an annealing process above 600 -C is necessary to obtain the L10-ordered structure in CoPtAg system. Such high-temperature treatments are undesirable for the manufacturing process. Previous study indicated that Cu addition is very effective to reduce the ordering temperature of L10-CoPt. The possible mechanism is that smaller Cu atoms diffuse into the CoPt crystal lattice, as a result, the crystal lattice has a small change owing to the formation of CoPtCu alloys. Thus, the activation energy for the disorder/ order transformation would be lowered. Can the Cu addition also help to reduce the ordering temperature of the above mentioned CoPtAg films but still keeping the (001) texture? To find the answer, we insert a very thin Cu layer between CoPt and Ag in every unit while depositing the multilayer precursors, leading to a little content (about 5% in atomic ratio) of Cu in the whole nanocomposite film after annealing. Shown in Fig. 3 are the XRD patterns of the Co32Pt35Cu5Ag28 film annealed at various temperatures for 30 min. With Cu additive, the CoPtAg film starts ordering at a lower annealing temperature of 450 -C, which is lower by 150 -C than the pure CoPtAg films. On the other hand, the
4. Conclusions CoPt/Ag nanocomposite films have been prepared by magnetron sputtering and subsequent annealing. The effect of Ag on the structure and magnetic properties of CoPt/Ag nanocomposite films was investigated. It was found that the existence of the Ag plays a dominant role in inducing the (001) texture of the film. (001) texture and a large perpendicular coercivity in the range of 5.6 –7.0 kOe have been achieved in the CoPtAg films after annealing at 600 -C. The Cu additive is very effective to reduce the ordering temperature in CoPtAg system. With little Cu additive, the CoPtAg films start ordering at a lower annealing temperature of 450 -C, which is lower by 150 -C than the pure CoPtAg films. A perpendicular orientation preferred Co32Pt35Cu5Ag28 nanocomposite film, with a low ordering temperature of 500 -C and a large perpendicular coercivity of 7.2 kOe, has been achieved successfully. Acknowledgements This work is supported in part by the National Nature Science Foundation of China under Grant No.50371056 and 60490291, Outstanding Yong Scientist Foundation of Hubei Province (2005ABB033), Excellent Creative Research Team Project of Hubei Province and Hubei University, Key project of Educational Department of Hubei Province (2004Z003), and the Research Grants Council of Hong Kong SAR (Ref. No. CUHK4182/04E). References [1] C. Chen, R. Sakurai, M. Hashimoto, J. Shi, Y. Nakamura, Thin Solid Films 459 (2004) 200. [2] V. Karanasos, I. Panagiotopoulos, D. Niarchos, J. Magn. Magn. Mater. 249 (2002) 471. [3] S. Stavroyiannis, I. Panagiotopoulos, D. Niarchos, J.A. Christodoulides, Y. Zhang, G.C. Hadjipanayis, Appl. Phys. Lett. 73 (1998) 3453. [4] H. Wang, S.P. Wong, W.Y. Cheung, N. Ke, M.F. Chiah, H. Liu, X.X. Zhang, J. Appl. Phys. 88 (2000) 2063. [5] V. Karanasos, I. Panagiotopoulos, D. Niarchos, Appl. Phys. Lett. 79 (2001) 1255. [6] C.P. Luo, S.H. Liou, L. Gao, Y. Liu, D.J. Sellmyer, Appl. Phys. Lett. 77 (2000) 2225.
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[7] C. Chen, O. Kitakami, S. Okamoto, Y. Shimada, Appl. Phys. Lett. 76 (2000) 3218. [8] H. Yamaguchi, O. Kitakami, S. Okamoto, Y. Shimada, K. Oikawa, K. Fukamichi, Appl. Phys. Lett. 79 (2001) 2001. [9] O. Kitakami, Y. Shimada, K. Oikawa, H. Daimon, K. Fukamichi, Appl. Phys. Lett. 78 (2001) 1104.
[10] T. Maeda, T. Kai, A. Kikitsu, T. Nagase, J. Akiyama, Appl. Phys. Lett. 80 (2002) 2147. [11] W.M. Liao, Y.P. Lin, F.T. Yuan, S.K. Chen, J. Magn. Magn. Mater. 272 (2004) 2175. [12] Y.N. Hsu, S. Jeong, D.E. Laughlin, J. Appl. Phys. 89 (2001) 7068.