自從龐磁電阻(CMR)物理現象發現以來，鈣鈦礦型錳氧化物的研究就成為了當今凝聚態物理學研究的熱點之一。這不僅是因為CMR效應在磁存儲技術領域具有潛在的應用價值，而且這類氧化物本身也蘊含著豐富的物理現象。本論文通過對鈣鈦礦型錳氧化物的A位和B位摻雜研究，對其結構、磁和電輸運性質進行了研究探索，主要工作概括如下：用固相燒結的方法成功製備了層狀鈣鈦礦錳氧化物(La,Sr)_3 Mn_(2-2x) A_2x O_7，(A=Al,Ti)多晶樣品。研究發現，在層狀鈣鈦礦(La,Sr)_3 Mn_2 O_7中，用Al或Ti替代Mn對其磁、電的性質影響非常顯著。隨溫度的降低，樣品表現出從順磁(PM)到鐵磁(FM)及自旋玻璃態(SG)等複雜的磁相變行為。電性測量表明，在(La,Sr)_3 Mn_2 O_7中摻雜一點的Al，整個觀察的溫區內都表現出絕緣體或半導體的性質。我們也準備了層狀鈣鈦礦R_(2-x) SrNa_x Mn_2 O_7，(R=Pr,Sm)多晶樣品，研究了其磁性。在低溫時，樣品中鐵磁態和反鐵磁態並存。實驗結果顯示，Sm^(3+)或 Pr^(3+)被Na^+離子取代，改變了陽離子的平均半徑以及結構中錳與氧的相對位置，使得Mn^(4+)-O-Mn^(3+)鍵角更小而減弱雙交換作用。我們也發現到Sm_(2-x) SrNa_x Mn_2 O_7樣品的溫度在T_c溫度附近可以觀察到磁性轉變及一級相變的現象。

Because of the potential applications of CMR effect in magnetic random access memories, and many physical properties observed in the manganite with a perovskite structure, it has been attracted a lot of attention in condensed matter physics since the discovery of the colossal magnetoresistance(CMR) phenomenon. We study the structures, magnetic and electrical transport properties of the perovskite manganites through doping on the A-site and B-site independently. The main results are generalized as follows. A series of polycrystalline Al-doped and Ti-doped Ruddlesden-Popper manganates (La,Sr)_3 Mn_(2-2x) A_2x O_7 (A=Al or Ti) are synthesized by the solid state reaction method. The effect of Al doping or Ti doping on the magnetic and transport properties is investigated. With the decrease of temperature, the system undergoes a transition from paramagnetism to the long-range ferromagnetic order and further to spin glass state. It is found that Al substitution for Mn greatly affects the magnetic and electrical properties of the parent phase (La,Sr)_3 Mn_2 O_7. A little Al dopant can lead to the samples showing semiconductor or insulator behaviour in the whole observed temperature range while the parent phase has a metal-insulator transition. We also prepare polycrystalline layered perovskite R_(2-x) SrNa_x Mn_2 O_7，(R=Pr,Sm), and investigate its magnetic properties. At low temperature, the FM and AFM phases coexist in the sample. Substitution of Sm^(3+)or Pr^(3+) by Na^+ results in the change of the average radius of the cation on A-site and the related position of manganese ion and oxygen ion, and then weakens the double exchange interaction (DE) of Mn^(4+)-O-Mn^(3+)couple. A first-order phase transition near Curie temperature Tc and metamagnetic transition at certain temperatures above Tc are observed in the sample.

[1] Si Ji-Wei, Cao Qing-Qi, Gu Ben-Xi and Du You-Wei (2005), Chin. Phys.,p. 14, 2118
[2] K. Cherif, S. Zemnib, J. Dhahri, M. Oumezzine, M. Said, H. Vincent (2007), Magnetocaloric effect in layered perovskite manganese oxide
La1.4(Sr1−xBax)1.6Mn2O7 (0≤x≤0.6) bulk materials, Journal of Alloys and Compounds, 432, pp.30–33
[3] MIRA J, RIVAS J, HUESO L E, RIVADULLA F, LOPENQUINTELA M A (2002), Drop of magnetocaloric effect related to thechange from first- to second-order magnetic phase transition inLa2/3(Ca1−xSrx)1/3MnO3[J], J Appl Phys, 91, pp. 8903−8906
[4] DAMAY F, MARTIN C, MAIGNAN A, RAVEAV B (1997), Cation disorder and size effects upon magnetic transitions in Ln0.5As0.5MnO3 manganites[J], J Appl Phys, 82(11), pp. 6181−3185
[5] Shang Jing-lin, Yuan Song-liu, Cao Heng, Wang Yong-qiang, Yin Shi-yan (2006), Effects of A-cation mismatch δ2 on transport properties of manganese doped oxide perovskite[J], Journal of the Chinese Rare Earth Society, 24(5), pp. 576−579,
[6] ZHONG W, CHENG W, DING W P, ZHANG N, DU Y W, YAN Q J. (1998), Magnetocaloric properties of Na-substituted perovskite-type manganese oxides[J]. Solid State Commun, 106(1), pp. 55−58
[7]亓淑豔、馬成國、董麗敏、韓志東、張顯友 (2009)，〝Na^+摻雜對鈣鈦礦La_0.7 Sr_(0.3-x) Na_x MnO_3的結構及磁熵變的影響〞，The Chinese Journal of
Nonferrous Metals, 19(5), pp. 894-899
[8] Hwang H. Y., Cheong S. W., Radaelli P. G., et al., (1995)Lattice effect on the magnetor - esistance indoped LaMnO3 [J ] ., Phys Rev Lett, 75(5), pp. 914-917
[9] Ren Qingbao (2004), Magnetoresistance Effect of Different Element Substitution in La2Site and Mn2Site of LaMnO3, JOURNAL OF XI′AN J IAOTON G UNIVERSITY, 38(6), pp. 645-648
[10] 盧盈靜 (2002)，〝鋇、鋁的添加對La_(2/3) Ca_(1/3) MnO_3之導電機構及磁阻效應之影響〞，p. 44，國立成功大學材料科學及工程學系
[11] P.G.deGenners (1960), physRev., 118, p. 141
[12] L. Liu , Z.C. Xia, S.L. Yuan (2006), Electrical transport and magnetic properties of La4/3Sr5/3Mn2O7., Materials Science and Engineering B, 127,p. 55–57
[13] Hong Zhu, XiaoJun Xu, Li Pi, and YuHeng Zhang (2000), Two-dimensional magnetic correlation and transport behavior of layered manganite La1.4Sr1.6Mn2-xCuxO7, 62(10), pp. 6754-6759
[14] T. G. Perring, G. Aeppli, Y. Moritomo, and Y. Tokura. (1996), Antiferromagnetic Short Range Order in a Two-Dimensional Manganite Exhibiting Giant Magnetoresistance, Phys Rev Lett, 78(16), pp. 3197-3200
[15] T. Kimura, A. Asamitsu, Y. Tomioka, and Y. Tokura (1997), Pressure-Enhanced Interplane Tunneling Magnetoresistance in a Layered Manganite Crystal, Phys Rev Lett, 79(19), p. 3722
[16] Ren-fu Yang, Young Sun, Nai-li Di, Qing-an Li, Zhao-hua Cheng (2007),
Anisotropic and large low-field magnetic entropy change in a La4/3Sr5/3Mn2O7 single crystal. Journal of Magnetism and Magnetic Materials, 309, pp. 149–152
[17] L.A. Han, C.L. Chen , H.Y. Dong, J.Y. Wang, G.M. Gao (2008), Effect of Al doping on the magnetic and electrical properties of layered perovskite La1.3Sr1.7Mn2_xAlxO7, Physica B, 403, p. 2614
[18] Aihua Wang , Guohui Cao (2006), Electron-transport and magnetic properties of the layered perovskite La2_2xSr1+2xMn2O7, Journal of Magnetism and Magnetic Materials, 305, p. 521
[19] Takeshi Murata, Tomoyuki Terai, Takashi Fukuda, Tomoyuki Kakeshita (2006), Phase boundary between uniaxial and planar ferromagnets in layered perovskite manganite La2_2xSr1+2xMn2O7 (0.313≤x≤0.350), Journal of Magnetism and Magnetic Materials, 303,pp. 138–141
[20] Aihua Wang, Tao Liu, Yang Liu, Guohui Cao (2005), The Jahn-Teller effect of layered perovskite manganites La2_2xSr1+2xMn2O7 studied by Mn K-edge XAFS, Physica B, 363, pp. 115–121
[21] Jun Zhang, Fangwei Wang, Panlin Zhang, Qiwei Yan (2000), Effect of lanthanide substitution on structure and magnetic properties in layered perovskite La1.2Sr1.8Mn2O7, Materials Science and Engineering B, 76, pp. 6–9
[22] K. Hirota, S. Ishihara, H. Fujioka, M. Kubota, H. Yoshizawa, Y. Moritomo, Y. Endoh, and S. Maekawa (2002), Spin dynamical properties and orbital states of the layered perovskite La2-2xSr1+2xMn2O7 .(0.3≤x≤0.5)., PHYSICAL REVIEW B, 65, 064414-1
[23] H. Meskine, Z. S. Popovic´, and S. Satpathy (2002), Electronic structure and exchange interaction in the layered perovskite Sr3Mn2O7, PHYSICAL REVIEW B, 65, 094402
[24] H. Asano, J. Hayakawa, and M. Matsui (1997), Magnetoresistance in thin films and bulks of layered-perovskite La2-2xCa1+2xMn2O7, Appl. Phys. Lett., 70(17) pp.2303-2305
[25] H. Asano, J. Hayakawa, and M. Matsui (1997), Two-dimensional ferromagnetic ordering and magnetoresistance in the layered perovskite La2-2xCa1+2xMn2O7, PHYSICAL REVIEW B, 56(9) pp.5395-5400
[26] Y. Moritomo, A. Asamitsu, H. Kuwahara, and Y. Tokura (1996), Giant magnetoresistance of manganese oxides with a layered perovskite structure, nature, 380(14) pp.141-144
[27] C. Zenner (1951), Phys. Rev.,82 ,p.403.
[28] Y. Tokura, et al. (1996), J. Appl.Phys., 79 ,p.5288
[29] R. Mahesh, R.Mahendiran, A.K. Raychaudhuri, C.N.R. Rao(1995)Solid State Chem.114, p.297
[30] A. Maignan, Ch. Simon, V. Caignaert, et al.(1995),SolidState Commun., 96, p.62
[31] L.M.Rodriguez-Martinez, J.P.Attfie(1996), Phys.Rev.B, 54, p.1562
[32] F.Damay, C.Martin, A.Maignan, B.Raveau(1997) J.APPI.Phys., 82 ,p.6181
[33] A.Maignan,C.Martin, F.Damay, B.Raveau(1998), Chem.Mater., 10, p.95
[34] Y.Tokura, in Cotossal Magnetoresistive Oxodes,Edited by Y.Tokura (Gordon And Breaeh Seienee Publishers ) P.ll ,(2000)
[35] 楊鴻昌(2002), 最敏感的感測元件SQUID及其前瞻性應用, 物理雙月刊,24(5) ,p. 653