- Email: [email protected]
core nanocable arrays
Materials Letters 122 (2014) 58–61
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Synthesis and magnetic properties of Ni/Fe shell/core nanocable arrays Xiaoru Li a,n, Peidong Li a, Guojun Song a, Zhi Peng a, Shengyu Feng b, Chuanjian Zhou b a b
Institute of Polymer Materials, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, PR China Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Jinan 250100, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 29 November 2013 Accepted 26 January 2014 Available online 1 February 2014
Ordered Ni/Fe shell/core structured nanocable arrays were successfully fabricated by a two-step electrodeposition process. Firstly, nickel (Ni) nanotubes were prepared by electrodeposition in nanoporous of anodic aluminum oxide (AAO) template. Then the AAO/Ni nanotube composite membrane was used as a secondary template to deposit Ferrum (Fe) nanowires into Ni nanotubes. The morphology and microstructure of the nanocables was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The chemical composition of the nanocables was confirmed by X-ray diffraction (XRD). Magnetization measurements revealed that Ni/Fe nanocable arrays have a lower remanence ratio than Ni nanotube and Fe nanowire arrays respectively. & 2014 Elsevier B.V. All rights reserved.
Keywords: Nanocable Nanotube Electrodeposition AAO template Magnetic Properties Magnetic materials
1. Introduction Attention has been paid over the last decade to the diverse physical performance of one-dimensional nanostructured materials due to their wide range of applications in optics, high-density perpendicular magnetic recording media and various sensor devices [1–5]. Compared with other methods such as sputtering [6], ball milling [7] and electroplating [8–10], template synthesis has been deemed to versatile approach of diverse nanostructured materials at a low cost [11–13]. Currently, ferromagnetic nanostructured materials, such as Fe [14], Co [15] and Ni [16], have been focused on research due to the unique magnetic properties [17]. Ordered ferromagnetic nanostructured arrays within a single magnetic domain size show a remarkably enhanced coercivity and a high remanence ratio, which make them prospective materials for magnetic recording media [18]. Some of the ferromagnetic nanostructured alloys can also enhance coercivity and remanence ratio. For example, Ni/Cu, Ni/Zn, and Ni/Pt nanowire arrays exhibit higher coercivity than Ni nanotubes [19–22]. However, highdensity perpendicular magnetic recording media not only has high coercivity but also demagnetization and stability performance. So it is necessary to prepare demagnetization materials. However, the literatures about two ferroelectric materials composite have been rarely reported. In this paper, we report the fabrication and magnetism of Ni/Fe shell/core nanocable arrays. Magnetization measurements revealed that Ni/Fe nanocable arrays have a lower remanence ratio than Ni
n
Corresponding author. E-mail address: [email protected] (X. Li).
0167-577X/$ - see front matter & 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2014.01.156
nanotube and Fe nanowire arrays respectively. The Ni/Fe nanocables have demagnetization performance, and they have potential applications in some magnetic-high-density perpendicular magnetic recording media. Given this, we infer that the degaussing phenomenon is related to the two magnetic materials.
2. Experimental section A porous anodic aluminum oxide (AAO) template (purchased from Whatman International Ltd.) with the pore diameter ranging from 180 to 250 nm and the depth ranging from 50 to 60 μm was used. In the experiment, Ni nanotube arrays were DC electrodeposited into the pores of AAO templates using a standard threeelectrode system. The side of the AAO membrane was sputtered with a thin layer of Au as a work electrode. A platinum film was used as the counter electrode and Ag/AgCl electrode in saturated KCl solution as the reference electrode. The pH of aqueous bath containing 0.6 M NiSO4 6H2O, 0.4 M H3BO3 and 0.3 M KCl was adjusted to 3. Electrodeposition was carried out at potential of 0.8 V/SCE for 15 min. And Ni nanotubes can be obtained. Then AAO/Ni nanotube composite membrane was used as a “secondary template”, and Fe nanowires were deposited into the Ni nanotubes from solution of 0.5 M FeSO4 7H2O, 0.5 M H3BO3 and 0.008 M ascorbic acid at the potential of 1.0 V/SCE for 20 min. Scanning electron microscopy (SEM; JEOL JSM-6390LV), transmission electron microscopy (TEM; CM200-FEG equipped with a GIF) were used to characterize the nanotubes, nanowires, and nanocables. Selected-area electron diffraction (SAED) pattern was used to determine the structure of the nanotubes, nanowires.
X. Li et al. / Materials Letters 122 (2014) 58–61
59
Fig. 1. (a) SEM image of Ni nanotube arrays; (b) TEM image of a single Ni nanotube and the inset is the corresponding SAED pattern; (c) SEM image of Fe nanowire arrays; and (d) TEM image of a Fe nanowire and the inset is the corresponding SAED pattern.
Fig. 2. (a) Typical SEM image of Ni/Fe nanocable; (b) An enlarged image in panel (a); (c) TEM image of a single solid Ni/Fe nanocable and the inset is the corresponding SAED pattern; and (d) Typical TEM image of a Ni/Fe nanocable with an open end.
60
X. Li et al. / Materials Letters 122 (2014) 58–61
3. Results and discussion
The chemical compositions of the nanocables were confirmed by X-ray diffraction (XRD; Bruker D8 Advance with a Cu-Kα radiation, λ ¼1.5418 Å). The magnetization measurements of the Ni/Cu nanocable arrays were carried out at room temperature on a vibrating sample magnetometer (VSM, Lakeshore 7307). 350
Fig. 1a shows a typical SEM image of Ni nanotube arrays after removing the AAO template with 3.0 mol/L NaOH solution. The highly ordered Ni nanotube arrays illustrate open and smooth ends clearly. The diameter of nanotubes is consistent with the AAO template pores. As shown in Fig. 1b, the TEM image shows that the Ni nanotube wall is uniform and thin—about 20 nm. The selected area electron diffraction (SAED) pattern presents concentric ringlike pattern, which is characteristic of polycrystalline. Fig. 1c shows the SEM image of Fe nanowire arrays. However, the surfaces of Fe nanowires are not smooth. The reason is that Fe nanowires exposed to damp situation get rusted after the removing of AAO template by use of 3.0 mol/L NaOH solution. The TEM image shows that the Fe nanowire is continuous (see Fig. 1d). The diameter equals to 200 nm approximately. The inset SAED pattern presents that the Fe nanowires are polycrystalline too. Fig. 2a and b present SEM images of the ordered Ni/Fe nanocable arrays after completely removing the AAO. The nanocables are uniform and stand parallel to each other. The deposition was carried at 0.8 V for Ni nanotubes and deposition time was for 15 min, and then at 1.0 V for Fe nanowires for 20 min. This embedded structure can keep Fe nanowire from rusting. A solid nanocable is seen from Fig. 2c, and the microstructure of outer shell (Ni nanotube) and inner core (Fe nanowire) can be observed vividly from the open end in Fig. 2c and d. The diameter of nanocable is about 250 nm. Furthermore, as shown in the inset of Fig. 2c, the corresponding SAED pattern presents Ni/Fe nanocables are also characteristic of polycrystalline. The XRD pattern (Fig. 3) of the nanocables embedded in the AAO template confirms Ni/Fe nanocable structure with the (111), (200), and (220) orientation of Ni, and (110), (200), and (211) orientation of Fe, respectively. Due to Au film sputtered on the bottom of AAO
Au (111)
300
Intensity (a.u.)
250 Ni (111) Fe (110)
200 150
Fe (200)
100
Ni (220) Fe (211)
Ni (200)
50 0 30
40
50
60
70
80
90
2θ (degree) Fig. 3. Typical XRD pattern of Ni/Fe nanocables inside the AAO template.
Table 1 Magnetic parameters of Ni nanotubes, Fe nanowires and Ni/Fe nanocables. Sample
Hm (Oe)
Hc (Oe)
ST
S?
Ni Fe Ni/Fe
4000 8000 7000
100 335 139
0.15 0.14 0.10
0.064 0.052 0.041
1.0
-------- H Ni nanotubes H // Ni nanotubes
0.5 M/Ms
M/Ms
0.5
0.0
0.0
-0.5
-0.5
-1.0
-1.0
-4000
H Fe nanowires H // Fe nanowires
1.0
-2000
0
2000
-10000
4000
-5000
H (Oe)
1.0
0
5000
10000
H(Oe)
H Ni/Fe nanocables H // Ni/Fe nanocables
M/Ms
0.5
0.0
-0.5
-1.0 -10000
-5000
0
5000
10000
H(Oe)
Fig. 4. (a) Magnetic hysteresis loops for Ni nanotube arrays; (b) Magnetic hysteresis loops for Fe nanowire arrays; and (c) Magnetic hysteresis loops for Ni/Fe nanocable arrays.
X. Li et al. / Materials Letters 122 (2014) 58–61
template, Au (111) reflection is indexed to the XRD pattern. All the nanocables show Ni–Fe phase-separated nanostructures. The magnetization behavior of Ni nanotubes, Fe nanowires and Ni/Fe nanocables were investigated. The magnetic parameters of the three samples are shown in Table 1. Fig. 4 displays the magnetization hysteresis (M–H) loops of Ni nanotube arrays, Fe nanowire arrays and Ni/Fe nanocable arrays. It can be seen that the squareness S (S¼Mr/Ms where Mr denotes remanence and Ms denotes the saturation magnetization) in the parallel direction is higher than that in the perpendicular direction, that is ST ¼0.15, S ? ¼ 0.064 for Ni nanotube arrays (see Fig. 4a); ST ¼0.14, S ? ¼0.052 for Fe nanowire arrays (see Fig. 4b); and ST ¼ 0.11, S ? ¼ 0.041 for Ni/Fe nanocable arrays(see Fig. 4c). In addition, it can be seen clearly that the squareness of the Ni/Fe nanocables is lower than that in Ni nanotube and Fe nanowire arrays. It indicates that Ni/Fe nanocables have lost their high coercivity due to demagnetization by neighboring magnetic domains. As seen from Table 1 and Fig. 4, Ni/Fe nanocables are more difficult to magnetize than Ni nanotubes and Fe nanowires. Because it is difficult to magnetize for Fe (110). Thus Ni/Fe nanocables lose their high coercivity because of coexistence of Ni and Fe. It can be explained by the magnetization of neighboring magnetic domains [20]. The discovery will make a contribution to conduct the preparation of the ferromagnetic nanocables and the research of magnetic properties. 4. Conclusions In summary, fabrication of ordered Ni/Fe nanocable arrays has been successfully carried out by electrodeposition in the pores of AAO template via a two-step deposition process. The characterization of morphology and chemical composition indicated the obtained Ni/Fe nanocable arrays. Magnetic hysteresis (M–H) loops have confirmed that magnetization direction is along the long axes of the nanotubes/nanowires. The phenomenon of demagnetization is a consequence for the magnetization of neighboring magnetic domains. These might be suitable for the preparation of the
61
ferromagnetic nanocables and the potential application of field weakening properties.
Acknowledgments This work was supported by the Specialized Research Fund for the Doctoral Program of the Ministry of Education (No. 20123706120003) and Foundation of Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, PR China. We thank for anonymous reviewers for their helpful suggestions on the quality improvement of our present paper. References [1] Almawlawi D, Coombs N, Moskovits M. J Appl Phys 1991;70:4421. [2] Yin LW, Bando YS, Zhan JH, Li MS, Golberg D. Adv Mater 2005;17:1972. [3] Thurn-Albrecht T, Schotter J, Kastle GA, Emley N, Shibauchi T, Krusin-Elbaum L, et al. Science 2000;290:2126. [4] Ai SF, Lu G, He Q, Li JB. J Am Chem Soc 2003;125:11140. [5] Fukunaka Y, Motoyama M, Konishi Y, Ishii R. Solid-State Lett 2006;9:C62. [6] Li XH, Yang Z. Mater Sci Eng B 2004;106:41. [7] Jartych E, Zurawicz JK, Oleszak D, Pekala MJ. Magn Magn Mater 2000;208:221. [8] Afshar A, Dolati AG, Ghorbani M. Mater Chem Phys 2002;77:352. [9] Ebrahimi F, Li H. Scr Mater 2006;55:263. [10] Ispas A, Matsushima H, Plieth W, Bund A. Electrochim Acta 2007;52:2785. [11] Martin CR. Adv Mater 1991;3:457. [12] Martin CR. Chem Mater 1996;8:1739. [13] Brumlik CJ, Menon VP, Martin CR. J Mater Res 1994;9:1174. [14] Cornejo DR, Padrόn-Hernάndez E. J Magn Magn Mater 2007;316:e48. [15] Ohgai T, Hoffer X, Fάbiάn A, Gravier L, Ansermet JJ. Mater Chem 2003;13:2530. [16] Li XR, Wang YQ, Song GJ, Peng Z, Yu YM, She XL, et al. Nanoscale Res Lett 2009;4:1015. [17] Yang SG, Zhu H, Yu DL, Jin ZQ, Tang SL, Du YW. J Magn Magn Mater 2000;222:97. [18] Liang HP, Guo YG, Hu JS, Zhu CF, Wan LJ, Bai CL. Inorg Chem 2005;44:3013. [19] Liu RS, Chang SC, Baginskiy I, Hu SF, Huang CY. Pramana – J Phys 2006;67:85. [20] Li XR, Wang YQ, Song GJ, Peng Z, Yu YM, She XL, et al. J Phys Chem C 2010;114:6914. [21] Sanjeev K, Vaishali S, Saroj A, Uttam KM, Ravinder KK. J Phys Chem C 2008;112:6531. [22] Liu LH, Li HT, Fan SH, Gu JJ, Li YP, Sun HY. J Magn Magn Mater 2009;321:3511.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Synthesis and magnetic properties of Ni/Fe shell/core nanocable arrays Xiaoru Li a,n, Peidong Li a, Guojun Song a, Zhi Peng a, Shengyu Feng b, Chuanjian Zhou b a b
Institute of Polymer Materials, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, PR China Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Jinan 250100, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 29 November 2013 Accepted 26 January 2014 Available online 1 February 2014
Ordered Ni/Fe shell/core structured nanocable arrays were successfully fabricated by a two-step electrodeposition process. Firstly, nickel (Ni) nanotubes were prepared by electrodeposition in nanoporous of anodic aluminum oxide (AAO) template. Then the AAO/Ni nanotube composite membrane was used as a secondary template to deposit Ferrum (Fe) nanowires into Ni nanotubes. The morphology and microstructure of the nanocables was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The chemical composition of the nanocables was confirmed by X-ray diffraction (XRD). Magnetization measurements revealed that Ni/Fe nanocable arrays have a lower remanence ratio than Ni nanotube and Fe nanowire arrays respectively. & 2014 Elsevier B.V. All rights reserved.
Keywords: Nanocable Nanotube Electrodeposition AAO template Magnetic Properties Magnetic materials
1. Introduction Attention has been paid over the last decade to the diverse physical performance of one-dimensional nanostructured materials due to their wide range of applications in optics, high-density perpendicular magnetic recording media and various sensor devices [1–5]. Compared with other methods such as sputtering [6], ball milling [7] and electroplating [8–10], template synthesis has been deemed to versatile approach of diverse nanostructured materials at a low cost [11–13]. Currently, ferromagnetic nanostructured materials, such as Fe [14], Co [15] and Ni [16], have been focused on research due to the unique magnetic properties [17]. Ordered ferromagnetic nanostructured arrays within a single magnetic domain size show a remarkably enhanced coercivity and a high remanence ratio, which make them prospective materials for magnetic recording media [18]. Some of the ferromagnetic nanostructured alloys can also enhance coercivity and remanence ratio. For example, Ni/Cu, Ni/Zn, and Ni/Pt nanowire arrays exhibit higher coercivity than Ni nanotubes [19–22]. However, highdensity perpendicular magnetic recording media not only has high coercivity but also demagnetization and stability performance. So it is necessary to prepare demagnetization materials. However, the literatures about two ferroelectric materials composite have been rarely reported. In this paper, we report the fabrication and magnetism of Ni/Fe shell/core nanocable arrays. Magnetization measurements revealed that Ni/Fe nanocable arrays have a lower remanence ratio than Ni
n
Corresponding author. E-mail address: [email protected] (X. Li).
0167-577X/$ - see front matter & 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2014.01.156
nanotube and Fe nanowire arrays respectively. The Ni/Fe nanocables have demagnetization performance, and they have potential applications in some magnetic-high-density perpendicular magnetic recording media. Given this, we infer that the degaussing phenomenon is related to the two magnetic materials.
2. Experimental section A porous anodic aluminum oxide (AAO) template (purchased from Whatman International Ltd.) with the pore diameter ranging from 180 to 250 nm and the depth ranging from 50 to 60 μm was used. In the experiment, Ni nanotube arrays were DC electrodeposited into the pores of AAO templates using a standard threeelectrode system. The side of the AAO membrane was sputtered with a thin layer of Au as a work electrode. A platinum film was used as the counter electrode and Ag/AgCl electrode in saturated KCl solution as the reference electrode. The pH of aqueous bath containing 0.6 M NiSO4 6H2O, 0.4 M H3BO3 and 0.3 M KCl was adjusted to 3. Electrodeposition was carried out at potential of 0.8 V/SCE for 15 min. And Ni nanotubes can be obtained. Then AAO/Ni nanotube composite membrane was used as a “secondary template”, and Fe nanowires were deposited into the Ni nanotubes from solution of 0.5 M FeSO4 7H2O, 0.5 M H3BO3 and 0.008 M ascorbic acid at the potential of 1.0 V/SCE for 20 min. Scanning electron microscopy (SEM; JEOL JSM-6390LV), transmission electron microscopy (TEM; CM200-FEG equipped with a GIF) were used to characterize the nanotubes, nanowires, and nanocables. Selected-area electron diffraction (SAED) pattern was used to determine the structure of the nanotubes, nanowires.
X. Li et al. / Materials Letters 122 (2014) 58–61
59
Fig. 1. (a) SEM image of Ni nanotube arrays; (b) TEM image of a single Ni nanotube and the inset is the corresponding SAED pattern; (c) SEM image of Fe nanowire arrays; and (d) TEM image of a Fe nanowire and the inset is the corresponding SAED pattern.
Fig. 2. (a) Typical SEM image of Ni/Fe nanocable; (b) An enlarged image in panel (a); (c) TEM image of a single solid Ni/Fe nanocable and the inset is the corresponding SAED pattern; and (d) Typical TEM image of a Ni/Fe nanocable with an open end.
60
X. Li et al. / Materials Letters 122 (2014) 58–61
3. Results and discussion
The chemical compositions of the nanocables were confirmed by X-ray diffraction (XRD; Bruker D8 Advance with a Cu-Kα radiation, λ ¼1.5418 Å). The magnetization measurements of the Ni/Cu nanocable arrays were carried out at room temperature on a vibrating sample magnetometer (VSM, Lakeshore 7307). 350
Fig. 1a shows a typical SEM image of Ni nanotube arrays after removing the AAO template with 3.0 mol/L NaOH solution. The highly ordered Ni nanotube arrays illustrate open and smooth ends clearly. The diameter of nanotubes is consistent with the AAO template pores. As shown in Fig. 1b, the TEM image shows that the Ni nanotube wall is uniform and thin—about 20 nm. The selected area electron diffraction (SAED) pattern presents concentric ringlike pattern, which is characteristic of polycrystalline. Fig. 1c shows the SEM image of Fe nanowire arrays. However, the surfaces of Fe nanowires are not smooth. The reason is that Fe nanowires exposed to damp situation get rusted after the removing of AAO template by use of 3.0 mol/L NaOH solution. The TEM image shows that the Fe nanowire is continuous (see Fig. 1d). The diameter equals to 200 nm approximately. The inset SAED pattern presents that the Fe nanowires are polycrystalline too. Fig. 2a and b present SEM images of the ordered Ni/Fe nanocable arrays after completely removing the AAO. The nanocables are uniform and stand parallel to each other. The deposition was carried at 0.8 V for Ni nanotubes and deposition time was for 15 min, and then at 1.0 V for Fe nanowires for 20 min. This embedded structure can keep Fe nanowire from rusting. A solid nanocable is seen from Fig. 2c, and the microstructure of outer shell (Ni nanotube) and inner core (Fe nanowire) can be observed vividly from the open end in Fig. 2c and d. The diameter of nanocable is about 250 nm. Furthermore, as shown in the inset of Fig. 2c, the corresponding SAED pattern presents Ni/Fe nanocables are also characteristic of polycrystalline. The XRD pattern (Fig. 3) of the nanocables embedded in the AAO template confirms Ni/Fe nanocable structure with the (111), (200), and (220) orientation of Ni, and (110), (200), and (211) orientation of Fe, respectively. Due to Au film sputtered on the bottom of AAO
Au (111)
300
Intensity (a.u.)
250 Ni (111) Fe (110)
200 150
Fe (200)
100
Ni (220) Fe (211)
Ni (200)
50 0 30
40
50
60
70
80
90
2θ (degree) Fig. 3. Typical XRD pattern of Ni/Fe nanocables inside the AAO template.
Table 1 Magnetic parameters of Ni nanotubes, Fe nanowires and Ni/Fe nanocables. Sample
Hm (Oe)
Hc (Oe)
ST
S?
Ni Fe Ni/Fe
4000 8000 7000
100 335 139
0.15 0.14 0.10
0.064 0.052 0.041
1.0
-------- H Ni nanotubes H // Ni nanotubes
0.5 M/Ms
M/Ms
0.5
0.0
0.0
-0.5
-0.5
-1.0
-1.0
-4000
H Fe nanowires H // Fe nanowires
1.0
-2000
0
2000
-10000
4000
-5000
H (Oe)
1.0
0
5000
10000
H(Oe)
H Ni/Fe nanocables H // Ni/Fe nanocables
M/Ms
0.5
0.0
-0.5
-1.0 -10000
-5000
0
5000
10000
H(Oe)
Fig. 4. (a) Magnetic hysteresis loops for Ni nanotube arrays; (b) Magnetic hysteresis loops for Fe nanowire arrays; and (c) Magnetic hysteresis loops for Ni/Fe nanocable arrays.
X. Li et al. / Materials Letters 122 (2014) 58–61
template, Au (111) reflection is indexed to the XRD pattern. All the nanocables show Ni–Fe phase-separated nanostructures. The magnetization behavior of Ni nanotubes, Fe nanowires and Ni/Fe nanocables were investigated. The magnetic parameters of the three samples are shown in Table 1. Fig. 4 displays the magnetization hysteresis (M–H) loops of Ni nanotube arrays, Fe nanowire arrays and Ni/Fe nanocable arrays. It can be seen that the squareness S (S¼Mr/Ms where Mr denotes remanence and Ms denotes the saturation magnetization) in the parallel direction is higher than that in the perpendicular direction, that is ST ¼0.15, S ? ¼ 0.064 for Ni nanotube arrays (see Fig. 4a); ST ¼0.14, S ? ¼0.052 for Fe nanowire arrays (see Fig. 4b); and ST ¼ 0.11, S ? ¼ 0.041 for Ni/Fe nanocable arrays(see Fig. 4c). In addition, it can be seen clearly that the squareness of the Ni/Fe nanocables is lower than that in Ni nanotube and Fe nanowire arrays. It indicates that Ni/Fe nanocables have lost their high coercivity due to demagnetization by neighboring magnetic domains. As seen from Table 1 and Fig. 4, Ni/Fe nanocables are more difficult to magnetize than Ni nanotubes and Fe nanowires. Because it is difficult to magnetize for Fe (110). Thus Ni/Fe nanocables lose their high coercivity because of coexistence of Ni and Fe. It can be explained by the magnetization of neighboring magnetic domains [20]. The discovery will make a contribution to conduct the preparation of the ferromagnetic nanocables and the research of magnetic properties. 4. Conclusions In summary, fabrication of ordered Ni/Fe nanocable arrays has been successfully carried out by electrodeposition in the pores of AAO template via a two-step deposition process. The characterization of morphology and chemical composition indicated the obtained Ni/Fe nanocable arrays. Magnetic hysteresis (M–H) loops have confirmed that magnetization direction is along the long axes of the nanotubes/nanowires. The phenomenon of demagnetization is a consequence for the magnetization of neighboring magnetic domains. These might be suitable for the preparation of the
61
ferromagnetic nanocables and the potential application of field weakening properties.
Acknowledgments This work was supported by the Specialized Research Fund for the Doctoral Program of the Ministry of Education (No. 20123706120003) and Foundation of Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, PR China. We thank for anonymous reviewers for their helpful suggestions on the quality improvement of our present paper. References [1] Almawlawi D, Coombs N, Moskovits M. J Appl Phys 1991;70:4421. [2] Yin LW, Bando YS, Zhan JH, Li MS, Golberg D. Adv Mater 2005;17:1972. [3] Thurn-Albrecht T, Schotter J, Kastle GA, Emley N, Shibauchi T, Krusin-Elbaum L, et al. Science 2000;290:2126. [4] Ai SF, Lu G, He Q, Li JB. J Am Chem Soc 2003;125:11140. [5] Fukunaka Y, Motoyama M, Konishi Y, Ishii R. Solid-State Lett 2006;9:C62. [6] Li XH, Yang Z. Mater Sci Eng B 2004;106:41. [7] Jartych E, Zurawicz JK, Oleszak D, Pekala MJ. Magn Magn Mater 2000;208:221. [8] Afshar A, Dolati AG, Ghorbani M. Mater Chem Phys 2002;77:352. [9] Ebrahimi F, Li H. Scr Mater 2006;55:263. [10] Ispas A, Matsushima H, Plieth W, Bund A. Electrochim Acta 2007;52:2785. [11] Martin CR. Adv Mater 1991;3:457. [12] Martin CR. Chem Mater 1996;8:1739. [13] Brumlik CJ, Menon VP, Martin CR. J Mater Res 1994;9:1174. [14] Cornejo DR, Padrόn-Hernάndez E. J Magn Magn Mater 2007;316:e48. [15] Ohgai T, Hoffer X, Fάbiάn A, Gravier L, Ansermet JJ. Mater Chem 2003;13:2530. [16] Li XR, Wang YQ, Song GJ, Peng Z, Yu YM, She XL, et al. Nanoscale Res Lett 2009;4:1015. [17] Yang SG, Zhu H, Yu DL, Jin ZQ, Tang SL, Du YW. J Magn Magn Mater 2000;222:97. [18] Liang HP, Guo YG, Hu JS, Zhu CF, Wan LJ, Bai CL. Inorg Chem 2005;44:3013. [19] Liu RS, Chang SC, Baginskiy I, Hu SF, Huang CY. Pramana – J Phys 2006;67:85. [20] Li XR, Wang YQ, Song GJ, Peng Z, Yu YM, She XL, et al. J Phys Chem C 2010;114:6914. [21] Sanjeev K, Vaishali S, Saroj A, Uttam KM, Ravinder KK. J Phys Chem C 2008;112:6531. [22] Liu LH, Li HT, Fan SH, Gu JJ, Li YP, Sun HY. J Magn Magn Mater 2009;321:3511.