BiFeO_3基多铁材料结构相变、热膨胀与磁电效应研究
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摘要
由于多铁性材料BiFeO3具有存在磁电耦合效应的特性,在磁存储介质等方面具有潜在的应用价值,因此成为当前材料学、物理学等学科的研究热点之一。在本文中,针对BiFeO3基陶瓷研究中的难点和热点,研究了BiFeO3反应烧结的相变过程、离子掺杂BiFeO3的磁电效应、以及离子掺杂BiFeO3基陶瓷的结构相变和热力学膨胀性质,主要取得了如下结果：1、BiFeO3二元体系反应烧结相变研究
以BiFeO3的反应烧结过程为研究对象,采用高温X射线衍射技术(HT-XRD)系统的研究了不同Bi2O3/Fe2O3配比下,不同升温速率下Bi2O3-Fe2O3二元体系在空气条件下动态的高温相变过程,以及不同降温速率下反应产物的热力学稳定性。结果表明,原料Bi2O3必须全部由斜方转变为立方后才能与Fe2O3发生反应,反应温度在700-800℃之间时部分Bi2O3和Fe2O3开始反应生成BiFeO3,当反应温度达到800℃时开始生成Bi2Fe4O9、Bi25FeO39等杂相,并且此时Fe2O3尚未完全反应。Bi203过量3%时,产物中BiFeO3的含量最高。升温速率越快,产物中主相BiFeO3含量越高,杂相BiFeO3含量越少,这或许与BiFeO3、 Bi2Fe4O9、Bi25FeO39的成核条件,BiFeO3的分解以及三种杂相之间的相互转化有关。BiFeO3、Bi2Fe4O9、Bi25Fe039三元体系在900-600℃之间处于热力学不稳定状态,BiFe03的亚稳定性使得反应产物中杂相Bi2Fe4O9、Bi25FeO39的含量与降温速率密切相关。2、离子掺杂BiFeO3的磁电效应研究
a)采用改进的固相烧结工艺制备出单相Bi1-2.5xPr1.5xBa0.5xFeO3(x=0.05,0.1)陶瓷,系统地研究了其结构、磁学和电学性质。x=0.1的样品发生了从菱形R3c到立方Pm3m的结构相变。局部结构畸变和螺旋自旋结构崩塌分别导致样品的磁性能大幅增加,同时发现以1：1的Pr4+和Ba2+离子同时替代BiFeO3中的Bi3+离子,抑制了Fe4+离子的产生,补偿了系统中的电荷缺陷,并发现这种电荷补偿能够有效的降低Bi1-2.5xPr1.5xBa0.5xFeO3样品的磁性,从而证明电荷缺陷是多铁性材料磁性的来源之一。Pr的掺杂导致样品结合能从5.72eV迅速降低到0.18eV,破坏了样品的铁电性。
b)系统地研究了单相Bi0.8-xPrxBa0.2FeO3(x≤0.1)陶瓷的结构、磁学和电学性质。所有样品都保持立方Pm3m结构,Pr的掺杂并未改变(BiBa)FeO3的晶胞对称性,只是单调地减小了其晶胞参数和晶胞体积。Pr掺杂引起的Fe06八面体的旋转导致了样品螺旋自旋结构的崩塌,从而大幅提高了其磁性。此外,还发现晶胞中Fe离子和Pr离子磁矩的耦合成为随着Pr掺杂量的增加样品剩余磁化强度(Mr)单调增加的原因,并且首次研究了其输运性质,指出其导电性能的增加导致了样品的漏电现象。3、离子掺杂BiFeO3的结构相变与热力学膨胀性质研究
采用高温X射线衍射的方法研究了单相Bi1-2.5xPr1.5xBa0.5xFeO3(x=0.05,0.1)陶瓷从室温25℃至800℃的结构相变过程及其热力学性质,指出Bi0.875Pr0.075Ba0.05FeO3样品在600-700℃之间发生了从菱形到立方结构的相变,该结构相变来源于材料不稳定的畸变钙钛矿R3c结构。同时还发现在该高温过程中样品几乎不分解,这表明Pr和Ba离子的共同掺杂使得BiFeO3的结构更加稳定。此外,通过不同温度下的晶格常数和晶胞体积的变化研究了样品的热力学膨胀性质,其表现出热力学各向同性及正膨胀行为,随着掺杂量的增加其平均热力学膨胀系数降低。对Bi0.75Pr0.15Ba0.1FeO3来说,高对称稳定的立方Pm3m结构使其在升温过程中不再发生相变并且降低了其热力学膨胀系数。此外在样品300-400℃之间热力学线性膨胀系数出现异常,这种异常或许来源于样品在Neel温度附近反铁磁向顺磁相的磁相变过程。
Multiferroic BiFeO3with magnetic and ferroelectric coupling property has become one of the hottest topics of physics and materials sciences on the current, which has great potential application in the memory storage device. In this work, the phase transition, thermal expansion and magnetoelectric effect on BiFeO3based multiferroic ceramics have been studied. The major interesting results can be summarized as follows.
1. The phase transition during the reaction sintering process of BiFeO3ceramics with different molar ratio of Bi2O3/Fe2O3and heating rate in air was studied via high temperature x-ray diffraction technique. And the thermal stability of BiFeO3, Bi25FeO39and Bi2Fe4O9ceramics with varying the cooling rate was also studied by such technique. Results show that the phase transition from monoclinic to cubic for Bi2O3was well done, which usually taken place at700-800℃. The Fe2O3did not react with Bi2O3to form BiFeO3until that transition finished. When the reaction temperature rose up to800℃, the impurity phases such as Bi25FeO39and Bi2Fe4O9synthesised simultaneously, more Fe2O3surpluses. The content of impurity phases mainly depend on the molar ratio of Bi2O3/Fe2O3, and1.03:1is optimum. Meanwhile it is indirect proportion to the heating rate, which may relat to the procedure of phase nucleation, decomposition and the transition between these phases. In addition, these phases are not in thermodynamic stable state during the cooling process between900-600℃. The content of impurity phases may relate to the cooling rate due to the metastability of BiFeO3.
2. a) Ba, Pr co-doped BiFeO3samples are synthesized by modified solid state reactions. The structural, magnetic, and ferroelectric properties of polycrystalline Bi1-2.5xPri.5XBao.5XFe03(x=0.05,0.1) ceramics are studied systematically. A structural phase transition of Rhombohedral-to-Cubic occurs in Bi0.75Pr0.15Ba0.1Fe03sample. The strong enhancement of the magnetization also confirmed that structural distortion and collapse of the spatial spin structure are the origin of spontaneous magnetization respectively. The co-doping of Ba and Pr in Bi1.2.5xPr1.5XBaxFe03samples, in which Ba2+and Pr4+molar proportion as1:1, can reduce the possible charge defects without the change of iron valence. Pr4+may compensate the charge, and decrease the magnetism of BFO, which confirms that charge defects are another origin of spontaneous magnetization. The band gap decreases sharply with Pr doping from5.72eV (x=0.05) to0.18eV (x=0.1), which destroy the ferroelectric property. b) The structural, magnetic, and ferroelectric properties of polycrystalline Bi0.8-xPrxBa0.2Fe03(x≤0.1) ceramics are studied systematically. The symmetry of the unit cell with Ba and Pr co-doping in BiFeO3in the doping range remains the cubic with the space group of Pm3m. The additive of Pr in (BiBa)FeO3reduces the unit cell volume together with varying the lattice parameters without changing the unit cell symmetry. The distortion of FeO6octahedron resulting from the additive of Pr may induce the local collapse of the spatial spin structure, which may enhance the spontaneous magnetization significantly. The remnant magnetization (Mr) increases monotonically with increasing the content of Pr, which probably originates from the ferromagnetic arrangement of Pr-ions and Fe-ions in the unit cell. The conductivity increases in a wide temperature regime result in an obvious leakage observed with increasing the Pr concentration.
3. The phase transition and thermal expansion of Bi1-2.5xPr1.5xBaxFe03(x=0.05,0.1) polycrystallines is studied by high temperature x-ray diffraction in the temperature range of25-800℃. A structural phase transition of Rhombohedral-to-Cubic occurs for Bio.875Pro.o75Bao.o5Fe03sample in the temperature of600-700℃, which may relate to its unstable rhombohedra distorted structure with the space group R3c. The rarely decomposition of these samples indicates that the Pr, Ba co-doped make the BiFeO3ceramics more stable. The thermal expansion determined by the temperature dependence of the unit-cell lattice parameters and volumes for Bi1-2.5xPr1.5xBaxFe03samples is also investigated, which shows an isotropic and positive behavior. The average thermal expansion coefficient decreases with increasing x. We argue that the cubic crystal structure with the high symmetrical of the space group Pm3m may be more stable for Bi0.75Pr0.15Bao.iFeO3sample, which may explain the reason why no phase transition occurs and its lower thermal expansion efficiencies. An obvious change in the slope of the linear fitted lines between300℃and400℃suggests a possible antiferromagnetic-paramagnetic transition, which occurs around the Neel temperature of the Bi1-2.5xPr1.5XBaxFe03samples.
以BiFeO3的反应烧结过程为研究对象,采用高温X射线衍射技术(HT-XRD)系统的研究了不同Bi2O3/Fe2O3配比下,不同升温速率下Bi2O3-Fe2O3二元体系在空气条件下动态的高温相变过程,以及不同降温速率下反应产物的热力学稳定性。结果表明,原料Bi2O3必须全部由斜方转变为立方后才能与Fe2O3发生反应,反应温度在700-800℃之间时部分Bi2O3和Fe2O3开始反应生成BiFeO3,当反应温度达到800℃时开始生成Bi2Fe4O9、Bi25FeO39等杂相,并且此时Fe2O3尚未完全反应。Bi203过量3%时,产物中BiFeO3的含量最高。升温速率越快,产物中主相BiFeO3含量越高,杂相BiFeO3含量越少,这或许与BiFeO3、 Bi2Fe4O9、Bi25FeO39的成核条件,BiFeO3的分解以及三种杂相之间的相互转化有关。BiFeO3、Bi2Fe4O9、Bi25Fe039三元体系在900-600℃之间处于热力学不稳定状态,BiFe03的亚稳定性使得反应产物中杂相Bi2Fe4O9、Bi25FeO39的含量与降温速率密切相关。2、离子掺杂BiFeO3的磁电效应研究
a)采用改进的固相烧结工艺制备出单相Bi1-2.5xPr1.5xBa0.5xFeO3(x=0.05,0.1)陶瓷,系统地研究了其结构、磁学和电学性质。x=0.1的样品发生了从菱形R3c到立方Pm3m的结构相变。局部结构畸变和螺旋自旋结构崩塌分别导致样品的磁性能大幅增加,同时发现以1：1的Pr4+和Ba2+离子同时替代BiFeO3中的Bi3+离子,抑制了Fe4+离子的产生,补偿了系统中的电荷缺陷,并发现这种电荷补偿能够有效的降低Bi1-2.5xPr1.5xBa0.5xFeO3样品的磁性,从而证明电荷缺陷是多铁性材料磁性的来源之一。Pr的掺杂导致样品结合能从5.72eV迅速降低到0.18eV,破坏了样品的铁电性。
b)系统地研究了单相Bi0.8-xPrxBa0.2FeO3(x≤0.1)陶瓷的结构、磁学和电学性质。所有样品都保持立方Pm3m结构,Pr的掺杂并未改变(BiBa)FeO3的晶胞对称性,只是单调地减小了其晶胞参数和晶胞体积。Pr掺杂引起的Fe06八面体的旋转导致了样品螺旋自旋结构的崩塌,从而大幅提高了其磁性。此外,还发现晶胞中Fe离子和Pr离子磁矩的耦合成为随着Pr掺杂量的增加样品剩余磁化强度(Mr)单调增加的原因,并且首次研究了其输运性质,指出其导电性能的增加导致了样品的漏电现象。3、离子掺杂BiFeO3的结构相变与热力学膨胀性质研究
采用高温X射线衍射的方法研究了单相Bi1-2.5xPr1.5xBa0.5xFeO3(x=0.05,0.1)陶瓷从室温25℃至800℃的结构相变过程及其热力学性质,指出Bi0.875Pr0.075Ba0.05FeO3样品在600-700℃之间发生了从菱形到立方结构的相变,该结构相变来源于材料不稳定的畸变钙钛矿R3c结构。同时还发现在该高温过程中样品几乎不分解,这表明Pr和Ba离子的共同掺杂使得BiFeO3的结构更加稳定。此外,通过不同温度下的晶格常数和晶胞体积的变化研究了样品的热力学膨胀性质,其表现出热力学各向同性及正膨胀行为,随着掺杂量的增加其平均热力学膨胀系数降低。对Bi0.75Pr0.15Ba0.1FeO3来说,高对称稳定的立方Pm3m结构使其在升温过程中不再发生相变并且降低了其热力学膨胀系数。此外在样品300-400℃之间热力学线性膨胀系数出现异常,这种异常或许来源于样品在Neel温度附近反铁磁向顺磁相的磁相变过程。
Multiferroic BiFeO3with magnetic and ferroelectric coupling property has become one of the hottest topics of physics and materials sciences on the current, which has great potential application in the memory storage device. In this work, the phase transition, thermal expansion and magnetoelectric effect on BiFeO3based multiferroic ceramics have been studied. The major interesting results can be summarized as follows.
1. The phase transition during the reaction sintering process of BiFeO3ceramics with different molar ratio of Bi2O3/Fe2O3and heating rate in air was studied via high temperature x-ray diffraction technique. And the thermal stability of BiFeO3, Bi25FeO39and Bi2Fe4O9ceramics with varying the cooling rate was also studied by such technique. Results show that the phase transition from monoclinic to cubic for Bi2O3was well done, which usually taken place at700-800℃. The Fe2O3did not react with Bi2O3to form BiFeO3until that transition finished. When the reaction temperature rose up to800℃, the impurity phases such as Bi25FeO39and Bi2Fe4O9synthesised simultaneously, more Fe2O3surpluses. The content of impurity phases mainly depend on the molar ratio of Bi2O3/Fe2O3, and1.03:1is optimum. Meanwhile it is indirect proportion to the heating rate, which may relat to the procedure of phase nucleation, decomposition and the transition between these phases. In addition, these phases are not in thermodynamic stable state during the cooling process between900-600℃. The content of impurity phases may relate to the cooling rate due to the metastability of BiFeO3.
2. a) Ba, Pr co-doped BiFeO3samples are synthesized by modified solid state reactions. The structural, magnetic, and ferroelectric properties of polycrystalline Bi1-2.5xPri.5XBao.5XFe03(x=0.05,0.1) ceramics are studied systematically. A structural phase transition of Rhombohedral-to-Cubic occurs in Bi0.75Pr0.15Ba0.1Fe03sample. The strong enhancement of the magnetization also confirmed that structural distortion and collapse of the spatial spin structure are the origin of spontaneous magnetization respectively. The co-doping of Ba and Pr in Bi1.2.5xPr1.5XBaxFe03samples, in which Ba2+and Pr4+molar proportion as1:1, can reduce the possible charge defects without the change of iron valence. Pr4+may compensate the charge, and decrease the magnetism of BFO, which confirms that charge defects are another origin of spontaneous magnetization. The band gap decreases sharply with Pr doping from5.72eV (x=0.05) to0.18eV (x=0.1), which destroy the ferroelectric property. b) The structural, magnetic, and ferroelectric properties of polycrystalline Bi0.8-xPrxBa0.2Fe03(x≤0.1) ceramics are studied systematically. The symmetry of the unit cell with Ba and Pr co-doping in BiFeO3in the doping range remains the cubic with the space group of Pm3m. The additive of Pr in (BiBa)FeO3reduces the unit cell volume together with varying the lattice parameters without changing the unit cell symmetry. The distortion of FeO6octahedron resulting from the additive of Pr may induce the local collapse of the spatial spin structure, which may enhance the spontaneous magnetization significantly. The remnant magnetization (Mr) increases monotonically with increasing the content of Pr, which probably originates from the ferromagnetic arrangement of Pr-ions and Fe-ions in the unit cell. The conductivity increases in a wide temperature regime result in an obvious leakage observed with increasing the Pr concentration.
3. The phase transition and thermal expansion of Bi1-2.5xPr1.5xBaxFe03(x=0.05,0.1) polycrystallines is studied by high temperature x-ray diffraction in the temperature range of25-800℃. A structural phase transition of Rhombohedral-to-Cubic occurs for Bio.875Pro.o75Bao.o5Fe03sample in the temperature of600-700℃, which may relate to its unstable rhombohedra distorted structure with the space group R3c. The rarely decomposition of these samples indicates that the Pr, Ba co-doped make the BiFeO3ceramics more stable. The thermal expansion determined by the temperature dependence of the unit-cell lattice parameters and volumes for Bi1-2.5xPr1.5xBaxFe03samples is also investigated, which shows an isotropic and positive behavior. The average thermal expansion coefficient decreases with increasing x. We argue that the cubic crystal structure with the high symmetrical of the space group Pm3m may be more stable for Bi0.75Pr0.15Bao.iFeO3sample, which may explain the reason why no phase transition occurs and its lower thermal expansion efficiencies. An obvious change in the slope of the linear fitted lines between300℃and400℃suggests a possible antiferromagnetic-paramagnetic transition, which occurs around the Neel temperature of the Bi1-2.5xPr1.5XBaxFe03samples.
引文
1 W. Kaczmarek and Z. Pajak, Sol Sta Commun.17:807(1975)
2 Yu. E. Roginskaya, Yu. Ya. Tomashpolskii, et al., Sov. Phys. JETP 23:47(1966)
3 Smolenskii G A, Chupis I. Sov Phys Usp.25:475-493 (1982)
4 Fischer P, Sosnowska I. J Phys C.15:4835(1982)
5王克峰,刘俊明,王雨,《科学通报》,53：1098-1135(2008)
6 Neaton J B, Ederer C, et al., Phys Rev B.71(1):014113-(1-8)(2005)
7 Teague J D, Gerson R, James W J. Sol. Sta. Commun.8(13):1073-1074(1970)
8 Bhattacharjee S.,Tripathi S.,Pandey D.App.Phy.Lett.91(4):042903(2007)
9 Kumar M.M., et al., J. Phys. Cond. Mater.11 (41):8131-8139(1999)
10 Cheon C.I.,Kim J.S.Jiang P.W., Jap. J. App.Phy.41(11):6777-6780(2002)
11 Park T J,Papaefthymiou G C,Viescas A J,et al.,Nano Lett.7(3):766-772(2007)
12 Shetty S,Palkar V R,pinto R. Pramana,58(5):1027-1030(2002)
13 Qian F ZJiang J S,Guo S Z,et al., J.Appl.Phys.106(8):084312-(1-6)(2009)
14 K. S. Nalwa, A. Garg, A.Upadhyaya, Matt.Lett.62:878-881(2008)
15 R.Palai,R.S.Katiyar,H.Schmid,et al.,Phy. Rev.B.77,014110.(2008)
16 E.I.Speranskaya, et al.,Bull.Acad.Sci.USSR,Div.Chem.Sic.5,874(1965)
17 Mahesh K.,Srinivas K.,et al.,Appl.Phys.Lett.76:2764(2000)
18 Y.P.Wang,L.Zhou,M.F.Zhang,et al.,App.Phy.Lett.,84:1731 (2004)
19 Pradhan A. K.,Kai Zhang,et al., J.Appl.Phys.97,093903(2005)
20 S.T.Zhang,M.H.Lu,D.Wu,Appl.Phy.Lett.87:262907(2005)
21 M. Thrall,R. Freer,C. Martin,et al., Jou. Euro.Cera. Society.28:2567(2008)
22 Sverre M.Selbach,Mari-Ann E.,Tor G.,Chem.Matter.21:169(2009)
23 Morozov M. I.,Lomanova N. A., Gusarov V. V.,Russ.J.Gen.Chem73:1676(2003)
24 J.K.Zhu,S.M.Feng, et al., High Pressure Res. Vol.30, No.2,265-272(2010)
25 Sverre M.Selbach, et al., J.Solid State Chem.183:1205-1208(2010)
26 Sverre M. Selbach, et al., Chem.Mater.21,169-173(2009)
27 J. R. Chen, W. L. Wang, et al., J. Alloys Compounds.459,66-70 (2008)
28 S. Bhattacharjee, K. Taji, et al., Phys. Rev.B.84,104116(2011)
29 J. Chen, X. R. Xing,et al., Appl. Phys. Lett 89,101914(2006)
30 S. N. Achary, S. J. Patwe, A. K. Tyagi, J. Alloys Compounds.461,474-480 (2008)
31 K. S. Nalwa, A. Garg, A. Upadhyaya, Mate.Lett.62,878-881 (2008)
32 Jun Zhang, M.A. Gondal, et al., J.Alloys Compounds.530,107-110, (2012)
33 Dinesh Varshney, Ashwini Kumar, J.Alloys Compounds.509,8421-8426 (2011)
34 D. Lebeuge, D. Colson, A. Forget, M. Viret, Phys. Rev. B.76,024116 (2007)
35 C.Ederer, N.A.Spaldin, Phys. Rev. B.71,060401(R) (2005)
36 Neeraj Kumara, Neeraj Panwarb, et al., J.Alloys Compounds.501,L29-L32(2010)
37 P Uniyal and K L Yadav, J. Phys.:Condens. Matter 21,405901(2009)
38 D.H.Wang,W.C.Goh,M.Ning,and C.K.Ong,Appl.Phys.Lett.88,212907(2006)
39 A. Gautam and V. S. Rangra, Cryst. Res. Technol.45, No.9,953-956 (2010)
40 Preetam Singh,J.H.Jung, Physica B 405:1086-1089(2010)
41 M. Mahesh Kumar, S. Srinath, et al., J.Magn. Magn. Mater.188-203 (1998)
42 V.A.Khomchenko,D.A.Kiselev,et al.,J.Appl.Phys.103,024150(2008)
43 Jie Wei, Raphael Haumont, et al.,Appl.Phys.Lett.96,102509(2010)
44马利静,郭烈锦,实验技术与管理,第28卷第11期：274-277(2011)
45 X.S. Wu, J. Gao, Physica. C313,79 (1999).
46 Q.Y. Xie, B. Lv, P.F. Wang, et al., Mater. Chem. Phys.114,636 (2009)
47 X.S. Wu, S.S. Jiang, N. Xu, et al.,Physica. C266,296 (1999).
48 Li J,Duan Y,He H and Song DJ.Alloys Compounds.315,259(2001)
49 Kundys B,Maignan A, et al.,Appl.Phys.Lett.92,112905(2008)
50 Hui Shen, Jiayue Xu, et al., Mater. Sci. Eng. B.157,77-80(2009)
51 W.Knafo, C.Meingast, et al., J. Magn. Magn. Mater.310,1248-1250(2007)
1 K. S. Nalwa, A. Garg, A.Upadhyaya, Mater. Lett.62:878-881(2008)
2王克峰,刘俊明,王雨,科学通报。第53卷第10期：1098-1135(2008)
3 R.Palai,R.S.Katiyar,H.Schmid,et al., Phy.Rev. B.77(1):014110-1-11(2008)
4 Mahesh Kumar M, Palkar V R, et al., App.Phy. Lett,.76:2764(2000)
5 Y. P. Wang,L. Zhou,M. F. Zhang, et al., App.Phy. Lett.84:1731(2004)
6 S.T.Zhang,M.H.Lu,D.Wu, et al., App.Phy. Lett.87:262907(2005)
7马利静,郭烈锦,实验技术与管理。第28卷第11期：274-277(2011)
8 M. Thrall,R. Freer,C. Martin,et al., Jou. Euro.Cera. Society.28:2567(2008)
9 Sverre M.Selbach,Mari-Ann Einarsrud, et al., Chem.Matter.21:169(2009)
10 Morozov M. I.,Lomanova N. A., Gusarov V. V., J.Gen.Chem.73:1676(2003)
1 Neeraj Kumara, Neeraj Panwarb, et al., J.Alloys Compounds.501,L29-L32(2010)
2 P Uniyal and K L Yadav, J. Phys.:Condens. Matter.21,405901 (2009)
3 D.H.Wang, W.C.Goh,M.Ning,and C.K.Ong,Appl.Phys.Lett.88,212907(2006)
4 A. Gautam and V. S. Rangra, Cryst. Res. Technol.45, No.9,953-956 (2010)
5 Jie Wei, Raphael Haumont, et al.,Appl.Phys.Lett.96,102509(2010)
6 C. Michel, J.-M. Moreau, et al.,Solid. State.Commun.7,701 (1969)
7 I Sosnowskat, et al., J. Phys. C:Solid State Phys..15:4835-4846(1982)
8 Li J,Duan Y,He H and Song D,J.Alloys Compounds.315,259(2001)
9 Kundys B,Maignan A, et al.,Appl.Phys.Lett.92,112905(2008)
10 X.S. Wu, J. Gao, Physica.C313,49 (1999).
11 Q.Y. Xie, B. Lv, P.F. Wang, et al., Mater. Chem. Phys.114,636 (2009)
12 X.S. Wu, S.S. Jiang, N. Xu, et al.,Physica. C266,296 (1999).
13 A. Gautam and V. S. Rangra, Cryst. Res. Technol.45, No.9,953-956 (2010)
14 Xingquan Zhang, Yu Sui, et al.,J. Appl. Phys.105,07D918 (2009)
15 V.A.Khomchenko,D.A.Kiselev,etal.,J.Appl.Phys.103,024150(2008)
16 M. Mahesh Kumar, S. Srinath, et al., J.Magn. Magn. Mater.188-203 (1998)
17 T. Matsui, H. Tanaka, et al., Appl. Phys. Lett.81,2764 (2002)
18 Qingyu Xu,Shengqiang Zhou, et al., J.Appl.Phys.107,093920(2010)
19 G. Catalan and J. F. Scott, Adv. Mater.21,2463 (2009)
20 J.J. Ge, X.B.Xue, G.F.Cheng et al., J. Magn. Magn. Mater.324 200-204 (2012)
21 C. Cascales, M. T. Fernandez-Daiz,et al.,Chem.Mater.14:1995-2003,(2002)
1 Qingyu Xu, Shengqiang Zhou, D.Wu, et al.,J.Appl.Phys.107,093920(2010)
2 D. H. Wang, W. C. Goh, M. Ning, C.K.Ong,Appl.Phys.Lett.88,212907(2006)
3 Neeraj Kumara, Neeraj Panwarb, et al., J.Alloys Compounds.501,L29-L32(2010)
4 K. S. Nalwa, A. Garg, A.Upadhyaya. Matt.Lett.62:878-881(2008)
5 D. Lebeuge, D. Colson, A. Forget, M. Viret, Phys. Rev. B.76,024116 (2007)
6 Y.P.Wang,L.Zhou,M.F.Zhang,et al,.App.Phy.Lett,84:1731 (2004)
7 C.Ederer, N.A.Spaldin, Phys. Rev. B.71,060401(R) (2005)
8 Preetam Singh,J.H.Jung, Physica B 405:1086-1089(2010)
9 Dinesh Varshney, Ashwini Kumar, J.Alloys Compounds.509,8421-8426 (2011)
10 Sverre M.Selbach,Mari-Ann E.,Tor G.,Chem.Matter.21:169(2009)
11 J. Chen, X. R. Xing,et al., Appl. Phys. Lett 89,101914(2006)
12 S. Bhattacharjee, K. Taji, et al., Phys. Rev.B.84,104116(2011)
13 J. R. Chen, W. L. Wang, et al., J. Alloys Compounds.459,66-70 (2008)
14 S. N. Achary, S. J. Patwe, A. K. Tyagi, J. Alloys Compounds.461,474-480 (2008)
15 Sverre M.Selbach,Mari-Ann E.,Tor G.,Chem.Matter.21:169(2009)
16 V.A.Khomchenko,D.A.Kiselev,et al., J.Appl.Phys.103,024150(2008)
17 Meera Keskar, K. Krishnan, et al., J. Alloys Compounds.458,104-108(2008)
18 R. V. Wandekar, B.N. Wani, et al., J. Alloys Compounds.433,84-90(2007)
19 Marita Kerstan, Christian Russel, Journal of power sources 196,7578-7584(2011)
20 M. Halvarsson, V. Langer, et al., Surface and coating tech.76-77,358-362(1995)
21 Hui Shen, Jiayue Xu, et al., Mater. Sci. Eng. B.157,77-80(2009)
22 W.Knafo, C.Meingast, et al., J. Magn. Magn. Mater.310,1248-1250(2007)
2 Yu. E. Roginskaya, Yu. Ya. Tomashpolskii, et al., Sov. Phys. JETP 23:47(1966)
3 Smolenskii G A, Chupis I. Sov Phys Usp.25:475-493 (1982)
4 Fischer P, Sosnowska I. J Phys C.15:4835(1982)
5王克峰,刘俊明,王雨,《科学通报》,53：1098-1135(2008)
6 Neaton J B, Ederer C, et al., Phys Rev B.71(1):014113-(1-8)(2005)
7 Teague J D, Gerson R, James W J. Sol. Sta. Commun.8(13):1073-1074(1970)
8 Bhattacharjee S.,Tripathi S.,Pandey D.App.Phy.Lett.91(4):042903(2007)
9 Kumar M.M., et al., J. Phys. Cond. Mater.11 (41):8131-8139(1999)
10 Cheon C.I.,Kim J.S.Jiang P.W., Jap. J. App.Phy.41(11):6777-6780(2002)
11 Park T J,Papaefthymiou G C,Viescas A J,et al.,Nano Lett.7(3):766-772(2007)
12 Shetty S,Palkar V R,pinto R. Pramana,58(5):1027-1030(2002)
13 Qian F ZJiang J S,Guo S Z,et al., J.Appl.Phys.106(8):084312-(1-6)(2009)
14 K. S. Nalwa, A. Garg, A.Upadhyaya, Matt.Lett.62:878-881(2008)
15 R.Palai,R.S.Katiyar,H.Schmid,et al.,Phy. Rev.B.77,014110.(2008)
16 E.I.Speranskaya, et al.,Bull.Acad.Sci.USSR,Div.Chem.Sic.5,874(1965)
17 Mahesh K.,Srinivas K.,et al.,Appl.Phys.Lett.76:2764(2000)
18 Y.P.Wang,L.Zhou,M.F.Zhang,et al.,App.Phy.Lett.,84:1731 (2004)
19 Pradhan A. K.,Kai Zhang,et al., J.Appl.Phys.97,093903(2005)
20 S.T.Zhang,M.H.Lu,D.Wu,Appl.Phy.Lett.87:262907(2005)
21 M. Thrall,R. Freer,C. Martin,et al., Jou. Euro.Cera. Society.28:2567(2008)
22 Sverre M.Selbach,Mari-Ann E.,Tor G.,Chem.Matter.21:169(2009)
23 Morozov M. I.,Lomanova N. A., Gusarov V. V.,Russ.J.Gen.Chem73:1676(2003)
24 J.K.Zhu,S.M.Feng, et al., High Pressure Res. Vol.30, No.2,265-272(2010)
25 Sverre M.Selbach, et al., J.Solid State Chem.183:1205-1208(2010)
26 Sverre M. Selbach, et al., Chem.Mater.21,169-173(2009)
27 J. R. Chen, W. L. Wang, et al., J. Alloys Compounds.459,66-70 (2008)
28 S. Bhattacharjee, K. Taji, et al., Phys. Rev.B.84,104116(2011)
29 J. Chen, X. R. Xing,et al., Appl. Phys. Lett 89,101914(2006)
30 S. N. Achary, S. J. Patwe, A. K. Tyagi, J. Alloys Compounds.461,474-480 (2008)
31 K. S. Nalwa, A. Garg, A. Upadhyaya, Mate.Lett.62,878-881 (2008)
32 Jun Zhang, M.A. Gondal, et al., J.Alloys Compounds.530,107-110, (2012)
33 Dinesh Varshney, Ashwini Kumar, J.Alloys Compounds.509,8421-8426 (2011)
34 D. Lebeuge, D. Colson, A. Forget, M. Viret, Phys. Rev. B.76,024116 (2007)
35 C.Ederer, N.A.Spaldin, Phys. Rev. B.71,060401(R) (2005)
36 Neeraj Kumara, Neeraj Panwarb, et al., J.Alloys Compounds.501,L29-L32(2010)
37 P Uniyal and K L Yadav, J. Phys.:Condens. Matter 21,405901(2009)
38 D.H.Wang,W.C.Goh,M.Ning,and C.K.Ong,Appl.Phys.Lett.88,212907(2006)
39 A. Gautam and V. S. Rangra, Cryst. Res. Technol.45, No.9,953-956 (2010)
40 Preetam Singh,J.H.Jung, Physica B 405:1086-1089(2010)
41 M. Mahesh Kumar, S. Srinath, et al., J.Magn. Magn. Mater.188-203 (1998)
42 V.A.Khomchenko,D.A.Kiselev,et al.,J.Appl.Phys.103,024150(2008)
43 Jie Wei, Raphael Haumont, et al.,Appl.Phys.Lett.96,102509(2010)
44马利静,郭烈锦,实验技术与管理,第28卷第11期：274-277(2011)
45 X.S. Wu, J. Gao, Physica. C313,79 (1999).
46 Q.Y. Xie, B. Lv, P.F. Wang, et al., Mater. Chem. Phys.114,636 (2009)
47 X.S. Wu, S.S. Jiang, N. Xu, et al.,Physica. C266,296 (1999).
48 Li J,Duan Y,He H and Song DJ.Alloys Compounds.315,259(2001)
49 Kundys B,Maignan A, et al.,Appl.Phys.Lett.92,112905(2008)
50 Hui Shen, Jiayue Xu, et al., Mater. Sci. Eng. B.157,77-80(2009)
51 W.Knafo, C.Meingast, et al., J. Magn. Magn. Mater.310,1248-1250(2007)
1 K. S. Nalwa, A. Garg, A.Upadhyaya, Mater. Lett.62:878-881(2008)
2王克峰,刘俊明,王雨,科学通报。第53卷第10期：1098-1135(2008)
3 R.Palai,R.S.Katiyar,H.Schmid,et al., Phy.Rev. B.77(1):014110-1-11(2008)
4 Mahesh Kumar M, Palkar V R, et al., App.Phy. Lett,.76:2764(2000)
5 Y. P. Wang,L. Zhou,M. F. Zhang, et al., App.Phy. Lett.84:1731(2004)
6 S.T.Zhang,M.H.Lu,D.Wu, et al., App.Phy. Lett.87:262907(2005)
7马利静,郭烈锦,实验技术与管理。第28卷第11期：274-277(2011)
8 M. Thrall,R. Freer,C. Martin,et al., Jou. Euro.Cera. Society.28:2567(2008)
9 Sverre M.Selbach,Mari-Ann Einarsrud, et al., Chem.Matter.21:169(2009)
10 Morozov M. I.,Lomanova N. A., Gusarov V. V., J.Gen.Chem.73:1676(2003)
1 Neeraj Kumara, Neeraj Panwarb, et al., J.Alloys Compounds.501,L29-L32(2010)
2 P Uniyal and K L Yadav, J. Phys.:Condens. Matter.21,405901 (2009)
3 D.H.Wang, W.C.Goh,M.Ning,and C.K.Ong,Appl.Phys.Lett.88,212907(2006)
4 A. Gautam and V. S. Rangra, Cryst. Res. Technol.45, No.9,953-956 (2010)
5 Jie Wei, Raphael Haumont, et al.,Appl.Phys.Lett.96,102509(2010)
6 C. Michel, J.-M. Moreau, et al.,Solid. State.Commun.7,701 (1969)
7 I Sosnowskat, et al., J. Phys. C:Solid State Phys..15:4835-4846(1982)
8 Li J,Duan Y,He H and Song D,J.Alloys Compounds.315,259(2001)
9 Kundys B,Maignan A, et al.,Appl.Phys.Lett.92,112905(2008)
10 X.S. Wu, J. Gao, Physica.C313,49 (1999).
11 Q.Y. Xie, B. Lv, P.F. Wang, et al., Mater. Chem. Phys.114,636 (2009)
12 X.S. Wu, S.S. Jiang, N. Xu, et al.,Physica. C266,296 (1999).
13 A. Gautam and V. S. Rangra, Cryst. Res. Technol.45, No.9,953-956 (2010)
14 Xingquan Zhang, Yu Sui, et al.,J. Appl. Phys.105,07D918 (2009)
15 V.A.Khomchenko,D.A.Kiselev,etal.,J.Appl.Phys.103,024150(2008)
16 M. Mahesh Kumar, S. Srinath, et al., J.Magn. Magn. Mater.188-203 (1998)
17 T. Matsui, H. Tanaka, et al., Appl. Phys. Lett.81,2764 (2002)
18 Qingyu Xu,Shengqiang Zhou, et al., J.Appl.Phys.107,093920(2010)
19 G. Catalan and J. F. Scott, Adv. Mater.21,2463 (2009)
20 J.J. Ge, X.B.Xue, G.F.Cheng et al., J. Magn. Magn. Mater.324 200-204 (2012)
21 C. Cascales, M. T. Fernandez-Daiz,et al.,Chem.Mater.14:1995-2003,(2002)
1 Qingyu Xu, Shengqiang Zhou, D.Wu, et al.,J.Appl.Phys.107,093920(2010)
2 D. H. Wang, W. C. Goh, M. Ning, C.K.Ong,Appl.Phys.Lett.88,212907(2006)
3 Neeraj Kumara, Neeraj Panwarb, et al., J.Alloys Compounds.501,L29-L32(2010)
4 K. S. Nalwa, A. Garg, A.Upadhyaya. Matt.Lett.62:878-881(2008)
5 D. Lebeuge, D. Colson, A. Forget, M. Viret, Phys. Rev. B.76,024116 (2007)
6 Y.P.Wang,L.Zhou,M.F.Zhang,et al,.App.Phy.Lett,84:1731 (2004)
7 C.Ederer, N.A.Spaldin, Phys. Rev. B.71,060401(R) (2005)
8 Preetam Singh,J.H.Jung, Physica B 405:1086-1089(2010)
9 Dinesh Varshney, Ashwini Kumar, J.Alloys Compounds.509,8421-8426 (2011)
10 Sverre M.Selbach,Mari-Ann E.,Tor G.,Chem.Matter.21:169(2009)
11 J. Chen, X. R. Xing,et al., Appl. Phys. Lett 89,101914(2006)
12 S. Bhattacharjee, K. Taji, et al., Phys. Rev.B.84,104116(2011)
13 J. R. Chen, W. L. Wang, et al., J. Alloys Compounds.459,66-70 (2008)
14 S. N. Achary, S. J. Patwe, A. K. Tyagi, J. Alloys Compounds.461,474-480 (2008)
15 Sverre M.Selbach,Mari-Ann E.,Tor G.,Chem.Matter.21:169(2009)
16 V.A.Khomchenko,D.A.Kiselev,et al., J.Appl.Phys.103,024150(2008)
17 Meera Keskar, K. Krishnan, et al., J. Alloys Compounds.458,104-108(2008)
18 R. V. Wandekar, B.N. Wani, et al., J. Alloys Compounds.433,84-90(2007)
19 Marita Kerstan, Christian Russel, Journal of power sources 196,7578-7584(2011)
20 M. Halvarsson, V. Langer, et al., Surface and coating tech.76-77,358-362(1995)
21 Hui Shen, Jiayue Xu, et al., Mater. Sci. Eng. B.157,77-80(2009)
22 W.Knafo, C.Meingast, et al., J. Magn. Magn. Mater.310,1248-1250(2007)
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