- Email: [email protected]
Structural, morphological and multiferroic properties of Pr and Co co-substituted BiFeO3 nanoparticles
Materials Letters 90 (2013) 152–155
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Structural, morphological and multiferroic properties of Pr and Co co-substituted BiFeO3 nanoparticles Xing’ao Li a,c,n, Xiwang Wang b, Yongtao Li c, Weiwei Mao b,c, Peng Li b, Tao Yang a, Jianping Yang c,nn a
Key Laboratory for Organic Electronics & Information Displays (KLOEID), Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China b School of Opto-Electronic Engineering, Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China c School of Science, Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 August 2012 Accepted 10 September 2012 Available online 18 September 2012
Single-phase Bi1 xPrxFeCo0.05O3 nanoparticles with varying x from 0 to 0.15 were prepared by sol–gel method.The effects of Pr substitution on the structures, magnetism and electrical properties of all the samples are investigated systematically. X-ray diffraction and Raman spectra results confirm that the samples simulated from a distorted rhombohedral structure to a cubic structure and surface morphology of the samples were examined by scanning electron microscope (SEM). The ferroelectric and magnetic hysteresis loops show coexistence of magnetism and ferroelectricity at room temperature. The structure transition may be the main cause for the origin of improved magnetic and ferroelectric properties. & 2012 Elsevier B.V. All rights reserved.
Keywords: Multiferroic Ferroelectric Magnetic Sol–gel Nanoparticles
1. Introduction BiFeO3(BFO) is the only single phase material which shows multiferroic phenomenon at room temperature having relatively high ferroelectric Curie temperature (TC 1100 K) and antiferromagnetic Ne´el temperature (TN 640 K) [1]. It possesses rhombohedrally distorted perovskite (ABO3) crystal structure with R3c space group [2]. BFO exhibits G-type antiferromagnetism due to the local spin ordering of Fe3 þ which forms a cycloidal spiral spin structure having spin periodicity of 62 nm [3]. The magnetic moments of ions rotate along the propagation direction of the modulated wave in the plane perpendicular to the hexagonal basal plane. The modulation inhibits the observation of weak ferromagnetism and of linear magnetoelectric effect [4]. Due to the existence of Fe2 þ and oxygen vacancies, BFO suffers from large leakage currents, which limits its applications. This limits the multifunctional applications of BFO as a dielectric [5]. In order to improve magnetic and electrical properties, partial substitution of rare-earth ions Pr3 þ at A-site Bi3 þ -ions, transition metal ion Co2 þ at B-site for Fe3 þ -ions or co-substitution with Pr/Mn, Pr/Sc,
n Corresponding author at: Key Laboratory for Organic Electronics & Information Displays (KLOEID), Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China. Tel.: þ86 258 5866 362; fax: þ86 25 858 66396. nn Corresponding author at: Institute of Physics (IP), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China. Tel.: þ86 25 858 66175. E-mail addresses: [email protected] (X. Li), [email protected] (J. Yang).
0167-577X/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2012.09.038
Pr/Ba/Co ions has been carried out [6–10]. Apparently, either the magnetic or the ferroelectric behavior has been improved. In this work, we prepare the single phase Bi1 xPrxFeCo0.05O3 (x ¼0, 0.05, 0.1, 0.15) nanoparticles by a tartaric acid modified the sol–gel method and report the structures, surface morphology, magnetic and electrical properties.
2. Experimental Single-phase Bi1 xPrxFeCo0.05O3 nanoparticles with varying x from 0 to 0.15 were prepared by the sol–gel method. Appropriate proportions of Pr6O11, Bi2O3, Co(NO3)2 6H2O and Fe(NO3)3 9H2O were used as starting materials and were dissolved in diluted nitric acid. Tartaric acid as an organic complex was put into the mixture. The mixture was stirred for 2–3 h. Then the gel was evaporated and dried at 250 1C to obtain the xerogel powder. The obtained powder was calcined at 550 1C for 2 h.
3. Results and discussion Fig. 1(a) shows the XRD patterns of the samples at room temperature. The XRD patterns confirmed single phase formation of x¼ 0–0.1 samples with no impurity peak. However, a few impurity peaks are observed in x¼0.15 sample. The diffraction peak positions show gradual variations in peaks. Fig. 1(b) reflections (104) and (110) are clearly separated in the x¼0 and x¼0.05 samples. Increasing x from 0 to 0.05, peak position of (104) reflection shifted toward a
X. Li et al. / Materials Letters 90 (2013) 152–155
153
Fig. 1. (a) X-ray diffraction patterns of Bi1 xPrxFeCo0.05O3 (x¼ 0, 0.05, 0.1, 0.15) nanoparticles. Enlarged view of the diffraction peaks (b) 2y ¼ 32 and (c) 2y ¼ 39.
Fig. 2. Raman spectra of all the samples measured at room temperature.
higher angle, while peak position of (110) reflection remained almost the same. However, from 0.05 to 0.1 doublet (104) and (110) merged to a single (110) peak. Fig. 1(c) shows the enlarged portion near diffraction angle 2y ¼39, where mergence of (006) and (202) peaks is evident. This shows a lattice distortion in rhombohedral structure from a distorted rhombohedral structure to a cubic structure with the space group Pm3m [10]. Similar type of behavior has also been reported for Pr/Ba co-doped and Mn doped BFO [10,11]. In order to better understand the crystal structures modified by Pr doped samples, the structural change of Pr doping is further reflected in the Raman spectra of the x ¼0–0.15 samples as shown in Fig. 2. The Raman spectra can confirm that the structures of x ¼0 are rhombohedral R3c [12]. From x ¼0 to x¼0.15, the spectral features show a drastic intensity reduction of A1-2 and A1-3 peaks, the A1-1and A1-2 gradually merge together, indicating the emergence of the orthorhombic phase. The gradually change of Raman spectra is consistent with the structural transition from rhombohedral to orthorhombic symmetry with increasing Pr content. These changes are attributed to a change in the local atomic structure due to the incorporation of Pr in the BiFeCo0.05O3 lattice. The combination of the Raman spectroscopy and the XRD data suggest that our samples are single-phase.
Fig. 3(a) shows SEM micrograph of the surface of x¼0 sample. Well-developed grains were observed in the SEM micrograph. The grain size is nonuniform which is estimated to be 1–2 mm. It is clear that the grains appear to stick to each other and agglomerate in small amount. For comparison purpose, SEM photograph of the x¼ 0.1 samples is shown in Fig. 3(b). Interestingly, with Pr doping the grain is agglomerated in a large number and the grain size was enlarged. Probably, Pr doping promoted grain growth which resulted in conglutination of each other and helped in densification. The systematic change in the magnetization (M) versus applied magnetic field (H) loops of the samples at room temperature are shown in Fig. 4. The magnetization curves of all the samples show weak ferromagnetic behavior at room temperature with no saturation even at an applied magnetic field of 15 kOe. From x ¼0 to x ¼0.1, the magnetic properties increase with increasing x respectively, while the most pronounced magnetic hysteresis loops were observed in the x¼ 0.1 samples. However, the Mr of x¼0.15(0.23 emu/g) is smaller than that of x ¼0.05 (0.28 emu/g) and x ¼0.1(0.34 emu/g), meanwhile it is also greater than that x ¼0 (0.19 emu/g). Noting the lattice distortion in rhombohedral structure of the samples with increasing Pr content, as shown from the XRD pattern above, the structure transition may therefore be the main cause for the origin of improved magnetic properties. The enhancement of magnetization in the samples is usually attributed to either the destruction of the spatially inhomogeneous spin-modulated incommensurate structure to release weak magnetization, or the increase of the spin canting angle resulting in the net macroscopic magnetization [13]. The structural phase transition from a distorted rhombohedral structure to a cubic structure occured in x¼0.1 sample leading to the collapse of the spatial spin structure [14]. So the most pronounced magnetic hysteresis loops were observed in the x¼0.1 samples. Raman spectra further indicates this conclusion, which shows that the gradual change of structural distortion is consistent from rhombohedral to orthorhombic symmetry with increasing Pr content. For x ¼0.15 samples, the possible explanation for the decrease of magnetic properties is charge on adding excessive Pr ions to BiFeCo0.05O3, while few impurity peaks were observed in the XRD patterns. The polarization hysteresis (P–E) loops of the samples under room temperature at 200 Hz are shown in Fig.5. All the samples show obvious P–E loops without much leakage effect, indicating that they are all well insulated. From x¼0 to x¼ 0.15, the remnant polarization (Pr) increased to a significant difference. Detail of the
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X. Li et al. / Materials Letters 90 (2013) 152–155
Fig. 3. SEM micrograph of the surface of Bi1 xPrxFeCo0.05O3 nanoparticles: (a) x ¼0 and (b) x¼ 0.1.
ferroelectric properties of Co doped BFO. We also note that the most pronounced polarization hysteresis loops were observed in the x ¼0.1 samples. The structural phase transition of the x¼0.1 sample from a distorted rhombohedral structure to a cubic structure with the space group Pm3m by Pr doping, as indicated by the XRD analysis and Raman spectra, would change the direction of the spontaneous polarization, which may therefore reduce the remnent polarization of these samples [15]. Namely, the great change in structure caused the strong enhancement of ferroelectric properties. Surprisingly, from x ¼0.1 to x ¼0.15 the ferroelectric properties rapidly changed again. The possible explanation for the decrease of ferroelectric properties are the few impurities which were observed in the XRD pattern, and Pr is nonferroelectric which dilutes the ferroelectric properties of x¼0.1 samples.
4. Conclusion Fig. 4. Magnetization hysteresis (M–H) loops of all the samples measured at room temperature.
In summary, single-phase Bi1 xPrxFeCo0.05O3 nanoparticles with varying x from 0 to 0.15 were prepared by the sol–gel method. We have studied the crystal structure, the magnetic and ferroelectric behavior of the nanoparticles. X-ray diffraction studies revealed a lattice distortion from a distorted rhombohedral structure to a cubic structure for x ¼0.1. The combination of the Raman spectroscopy and XRD data suggest that our samples are single-phase. It was also found that the doping of Pr improved magnetization and ferroelectric properties while the most pronounced mutations were observed in the x ¼0.1 samples.
Acknowledgments We acknowledge the financial support from the National Basic Research Program of China (2009CB930600, 2012CB933301), the Key Project of National High Technology Research of China (2011AA050526), the Ministry of Education of China (No. IRT1148), the National Natural Science Foundation of China (51172110,61106116), and the National Science Foundation of Jiangsu Province (BK2010525). References Fig. 5. Polarization hysteresis (P–E)loops of all the samples measured at room temperature.
changes as follows: x¼0.1 4 x ¼0 4 x¼0.15 4 x ¼0.05. From the results we can see obviously that only Co doped BFO exhibits good P–E loops. However, doping of a little amount of Pr significantly reduces the remnant polarization (Pr). This may be due to the fact that the Pr is nonferroelectric and dilutes the
[1] [2] [3] [4] [5]
Bhide VG, Multani MS. Solid State Commun 1965;3:271. Catalan G, Scott JF. Adv Mater 2009;21:2463. Sosnowska I, Neumaier TP, Steichele E. J Phys C 1982;15:4835. Ederer C, Spaldin NA. Phys Rev B 2005;71:060401. Qi X, Dho J, Tomov R, Blamire MG, MacManus-Driscoll. JL. Appl Phys Lett 2005;86:062903. [6] Wen Zheng, Lv Yong, Wu Di, Li Aidong. Appl Phys Lett 2011;99:012903. [7] Coondoo Indrani, Panwar Neeraj, Bdikin I, Puli VS, Katiyar RS, Kholkin AL. J Phys D: Appl Phys 2012;45:055302.
X. Li et al. / Materials Letters 90 (2013) 152–155
[8] Khomchenko VA, Troyanchuk IO, Karpinsky DV, Paixao. JA. J Mater Sci 2012;47:1578. [9] Xu Qingyu, Wen Zheng, Gao Jinlong, Wu Di, Tang Shaolong, Xu Mingxiang. Phys Rev B 2011;406:2025. [10] Cheng GF, Huang YH, Ge JJ, Lv B, Wu XS. J Appl Phys 2012;111:07C707. [11] Chauhan Sunil, Kumar Manoj, Chhoker Sandeep, Katyal SC, Singhb Hemant, Jewariya Mukesh, et al. Solid State Commun 2012;152:525.
155
[12] Haumont R, Kreisel J, Bouvier P, Hippert F. Phys Rev B 2006;73:132101. [13] Huang FZ, Lu XM, Lin WW, Wu XM, Kan Y, Zhu JS. Appl Phys Lett 2006;89:242914. [14] Zhang X, Sui Y, Wang X, Tang J, Su W. J Appl Phys 2009;105:07D918. [15] Ruette B, Zvyagin S, Pyatakov AP, Bush AA, Li JF, Belotelov VI, et al. Phys Rev B 2004;69:064114.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Structural, morphological and multiferroic properties of Pr and Co co-substituted BiFeO3 nanoparticles Xing’ao Li a,c,n, Xiwang Wang b, Yongtao Li c, Weiwei Mao b,c, Peng Li b, Tao Yang a, Jianping Yang c,nn a
Key Laboratory for Organic Electronics & Information Displays (KLOEID), Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China b School of Opto-Electronic Engineering, Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China c School of Science, Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 21 August 2012 Accepted 10 September 2012 Available online 18 September 2012
Single-phase Bi1 xPrxFeCo0.05O3 nanoparticles with varying x from 0 to 0.15 were prepared by sol–gel method.The effects of Pr substitution on the structures, magnetism and electrical properties of all the samples are investigated systematically. X-ray diffraction and Raman spectra results confirm that the samples simulated from a distorted rhombohedral structure to a cubic structure and surface morphology of the samples were examined by scanning electron microscope (SEM). The ferroelectric and magnetic hysteresis loops show coexistence of magnetism and ferroelectricity at room temperature. The structure transition may be the main cause for the origin of improved magnetic and ferroelectric properties. & 2012 Elsevier B.V. All rights reserved.
Keywords: Multiferroic Ferroelectric Magnetic Sol–gel Nanoparticles
1. Introduction BiFeO3(BFO) is the only single phase material which shows multiferroic phenomenon at room temperature having relatively high ferroelectric Curie temperature (TC 1100 K) and antiferromagnetic Ne´el temperature (TN 640 K) [1]. It possesses rhombohedrally distorted perovskite (ABO3) crystal structure with R3c space group [2]. BFO exhibits G-type antiferromagnetism due to the local spin ordering of Fe3 þ which forms a cycloidal spiral spin structure having spin periodicity of 62 nm [3]. The magnetic moments of ions rotate along the propagation direction of the modulated wave in the plane perpendicular to the hexagonal basal plane. The modulation inhibits the observation of weak ferromagnetism and of linear magnetoelectric effect [4]. Due to the existence of Fe2 þ and oxygen vacancies, BFO suffers from large leakage currents, which limits its applications. This limits the multifunctional applications of BFO as a dielectric [5]. In order to improve magnetic and electrical properties, partial substitution of rare-earth ions Pr3 þ at A-site Bi3 þ -ions, transition metal ion Co2 þ at B-site for Fe3 þ -ions or co-substitution with Pr/Mn, Pr/Sc,
n Corresponding author at: Key Laboratory for Organic Electronics & Information Displays (KLOEID), Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China. Tel.: þ86 258 5866 362; fax: þ86 25 858 66396. nn Corresponding author at: Institute of Physics (IP), Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210046, PR China. Tel.: þ86 25 858 66175. E-mail addresses: [email protected] (X. Li), [email protected] (J. Yang).
0167-577X/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2012.09.038
Pr/Ba/Co ions has been carried out [6–10]. Apparently, either the magnetic or the ferroelectric behavior has been improved. In this work, we prepare the single phase Bi1 xPrxFeCo0.05O3 (x ¼0, 0.05, 0.1, 0.15) nanoparticles by a tartaric acid modified the sol–gel method and report the structures, surface morphology, magnetic and electrical properties.
2. Experimental Single-phase Bi1 xPrxFeCo0.05O3 nanoparticles with varying x from 0 to 0.15 were prepared by the sol–gel method. Appropriate proportions of Pr6O11, Bi2O3, Co(NO3)2 6H2O and Fe(NO3)3 9H2O were used as starting materials and were dissolved in diluted nitric acid. Tartaric acid as an organic complex was put into the mixture. The mixture was stirred for 2–3 h. Then the gel was evaporated and dried at 250 1C to obtain the xerogel powder. The obtained powder was calcined at 550 1C for 2 h.
3. Results and discussion Fig. 1(a) shows the XRD patterns of the samples at room temperature. The XRD patterns confirmed single phase formation of x¼ 0–0.1 samples with no impurity peak. However, a few impurity peaks are observed in x¼0.15 sample. The diffraction peak positions show gradual variations in peaks. Fig. 1(b) reflections (104) and (110) are clearly separated in the x¼0 and x¼0.05 samples. Increasing x from 0 to 0.05, peak position of (104) reflection shifted toward a
X. Li et al. / Materials Letters 90 (2013) 152–155
153
Fig. 1. (a) X-ray diffraction patterns of Bi1 xPrxFeCo0.05O3 (x¼ 0, 0.05, 0.1, 0.15) nanoparticles. Enlarged view of the diffraction peaks (b) 2y ¼ 32 and (c) 2y ¼ 39.
Fig. 2. Raman spectra of all the samples measured at room temperature.
higher angle, while peak position of (110) reflection remained almost the same. However, from 0.05 to 0.1 doublet (104) and (110) merged to a single (110) peak. Fig. 1(c) shows the enlarged portion near diffraction angle 2y ¼39, where mergence of (006) and (202) peaks is evident. This shows a lattice distortion in rhombohedral structure from a distorted rhombohedral structure to a cubic structure with the space group Pm3m [10]. Similar type of behavior has also been reported for Pr/Ba co-doped and Mn doped BFO [10,11]. In order to better understand the crystal structures modified by Pr doped samples, the structural change of Pr doping is further reflected in the Raman spectra of the x ¼0–0.15 samples as shown in Fig. 2. The Raman spectra can confirm that the structures of x ¼0 are rhombohedral R3c [12]. From x ¼0 to x¼0.15, the spectral features show a drastic intensity reduction of A1-2 and A1-3 peaks, the A1-1and A1-2 gradually merge together, indicating the emergence of the orthorhombic phase. The gradually change of Raman spectra is consistent with the structural transition from rhombohedral to orthorhombic symmetry with increasing Pr content. These changes are attributed to a change in the local atomic structure due to the incorporation of Pr in the BiFeCo0.05O3 lattice. The combination of the Raman spectroscopy and the XRD data suggest that our samples are single-phase.
Fig. 3(a) shows SEM micrograph of the surface of x¼0 sample. Well-developed grains were observed in the SEM micrograph. The grain size is nonuniform which is estimated to be 1–2 mm. It is clear that the grains appear to stick to each other and agglomerate in small amount. For comparison purpose, SEM photograph of the x¼ 0.1 samples is shown in Fig. 3(b). Interestingly, with Pr doping the grain is agglomerated in a large number and the grain size was enlarged. Probably, Pr doping promoted grain growth which resulted in conglutination of each other and helped in densification. The systematic change in the magnetization (M) versus applied magnetic field (H) loops of the samples at room temperature are shown in Fig. 4. The magnetization curves of all the samples show weak ferromagnetic behavior at room temperature with no saturation even at an applied magnetic field of 15 kOe. From x ¼0 to x ¼0.1, the magnetic properties increase with increasing x respectively, while the most pronounced magnetic hysteresis loops were observed in the x¼ 0.1 samples. However, the Mr of x¼0.15(0.23 emu/g) is smaller than that of x ¼0.05 (0.28 emu/g) and x ¼0.1(0.34 emu/g), meanwhile it is also greater than that x ¼0 (0.19 emu/g). Noting the lattice distortion in rhombohedral structure of the samples with increasing Pr content, as shown from the XRD pattern above, the structure transition may therefore be the main cause for the origin of improved magnetic properties. The enhancement of magnetization in the samples is usually attributed to either the destruction of the spatially inhomogeneous spin-modulated incommensurate structure to release weak magnetization, or the increase of the spin canting angle resulting in the net macroscopic magnetization [13]. The structural phase transition from a distorted rhombohedral structure to a cubic structure occured in x¼0.1 sample leading to the collapse of the spatial spin structure [14]. So the most pronounced magnetic hysteresis loops were observed in the x¼0.1 samples. Raman spectra further indicates this conclusion, which shows that the gradual change of structural distortion is consistent from rhombohedral to orthorhombic symmetry with increasing Pr content. For x ¼0.15 samples, the possible explanation for the decrease of magnetic properties is charge on adding excessive Pr ions to BiFeCo0.05O3, while few impurity peaks were observed in the XRD patterns. The polarization hysteresis (P–E) loops of the samples under room temperature at 200 Hz are shown in Fig.5. All the samples show obvious P–E loops without much leakage effect, indicating that they are all well insulated. From x¼0 to x¼ 0.15, the remnant polarization (Pr) increased to a significant difference. Detail of the
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X. Li et al. / Materials Letters 90 (2013) 152–155
Fig. 3. SEM micrograph of the surface of Bi1 xPrxFeCo0.05O3 nanoparticles: (a) x ¼0 and (b) x¼ 0.1.
ferroelectric properties of Co doped BFO. We also note that the most pronounced polarization hysteresis loops were observed in the x ¼0.1 samples. The structural phase transition of the x¼0.1 sample from a distorted rhombohedral structure to a cubic structure with the space group Pm3m by Pr doping, as indicated by the XRD analysis and Raman spectra, would change the direction of the spontaneous polarization, which may therefore reduce the remnent polarization of these samples [15]. Namely, the great change in structure caused the strong enhancement of ferroelectric properties. Surprisingly, from x ¼0.1 to x ¼0.15 the ferroelectric properties rapidly changed again. The possible explanation for the decrease of ferroelectric properties are the few impurities which were observed in the XRD pattern, and Pr is nonferroelectric which dilutes the ferroelectric properties of x¼0.1 samples.
4. Conclusion Fig. 4. Magnetization hysteresis (M–H) loops of all the samples measured at room temperature.
In summary, single-phase Bi1 xPrxFeCo0.05O3 nanoparticles with varying x from 0 to 0.15 were prepared by the sol–gel method. We have studied the crystal structure, the magnetic and ferroelectric behavior of the nanoparticles. X-ray diffraction studies revealed a lattice distortion from a distorted rhombohedral structure to a cubic structure for x ¼0.1. The combination of the Raman spectroscopy and XRD data suggest that our samples are single-phase. It was also found that the doping of Pr improved magnetization and ferroelectric properties while the most pronounced mutations were observed in the x ¼0.1 samples.
Acknowledgments We acknowledge the financial support from the National Basic Research Program of China (2009CB930600, 2012CB933301), the Key Project of National High Technology Research of China (2011AA050526), the Ministry of Education of China (No. IRT1148), the National Natural Science Foundation of China (51172110,61106116), and the National Science Foundation of Jiangsu Province (BK2010525). References Fig. 5. Polarization hysteresis (P–E)loops of all the samples measured at room temperature.
changes as follows: x¼0.1 4 x ¼0 4 x¼0.15 4 x ¼0.05. From the results we can see obviously that only Co doped BFO exhibits good P–E loops. However, doping of a little amount of Pr significantly reduces the remnant polarization (Pr). This may be due to the fact that the Pr is nonferroelectric and dilutes the
[1] [2] [3] [4] [5]
Bhide VG, Multani MS. Solid State Commun 1965;3:271. Catalan G, Scott JF. Adv Mater 2009;21:2463. Sosnowska I, Neumaier TP, Steichele E. J Phys C 1982;15:4835. Ederer C, Spaldin NA. Phys Rev B 2005;71:060401. Qi X, Dho J, Tomov R, Blamire MG, MacManus-Driscoll. JL. Appl Phys Lett 2005;86:062903. [6] Wen Zheng, Lv Yong, Wu Di, Li Aidong. Appl Phys Lett 2011;99:012903. [7] Coondoo Indrani, Panwar Neeraj, Bdikin I, Puli VS, Katiyar RS, Kholkin AL. J Phys D: Appl Phys 2012;45:055302.
X. Li et al. / Materials Letters 90 (2013) 152–155
[8] Khomchenko VA, Troyanchuk IO, Karpinsky DV, Paixao. JA. J Mater Sci 2012;47:1578. [9] Xu Qingyu, Wen Zheng, Gao Jinlong, Wu Di, Tang Shaolong, Xu Mingxiang. Phys Rev B 2011;406:2025. [10] Cheng GF, Huang YH, Ge JJ, Lv B, Wu XS. J Appl Phys 2012;111:07C707. [11] Chauhan Sunil, Kumar Manoj, Chhoker Sandeep, Katyal SC, Singhb Hemant, Jewariya Mukesh, et al. Solid State Commun 2012;152:525.
155
[12] Haumont R, Kreisel J, Bouvier P, Hippert F. Phys Rev B 2006;73:132101. [13] Huang FZ, Lu XM, Lin WW, Wu XM, Kan Y, Zhu JS. Appl Phys Lett 2006;89:242914. [14] Zhang X, Sui Y, Wang X, Tang J, Su W. J Appl Phys 2009;105:07D918. [15] Ruette B, Zvyagin S, Pyatakov AP, Bush AA, Li JF, Belotelov VI, et al. Phys Rev B 2004;69:064114.