摻雜鈣鈦礦結構化合物的磁性和電輸運性質
發(fā)布時間：2019-06-27 11:39
【摘要】：鈣鈦礦類化合物(例如雙鈣鈦礦氧化物La2CoMnO6、有機鈣鈦礦CH3NH3PbI3等)具有豐富的物理特性。La2CoMn06具有較高的居里溫度、較大的磁電阻效應和介電常數(shù)·等,在磁學與自旋電子學及器件領域有廣泛研究與應用;CH3NH3PbI3具有優(yōu)良的光伏性能,是新型太陽能電池研究的熱點材料。離子摻雜是有效調控材料物理特性的重要手段之一,因此本論文用不同離子對La2CoMnO6中La位和Co位以及CH3NH3PbI3中Pb位進行摻雜,探討了離子摻雜對磁性與電性的影響機制。通過X射線衍射儀、掃描電子顯微鏡、PPMS等設備對樣品的晶體結構、表面形貌以及磁性和電輸運特性等進行了系統(tǒng)的研究。具體研究成果如下:1. La2CoMnO6鑭位摻雜Ca的磁性和電輸運性質的研究。用固相反應方法制備了多晶La2.xCaxCoMn06 (0≤x≤0.5)樣品,系統(tǒng)研究了 Ca2+離子摻雜對La2CoMnO6晶體結構、表面形貌、磁性、電性和磁電阻效應的影響。X射線衍射分析表明La位摻雜Ca2+離子保持了晶體單斜雙鈣鈦礦結構(空間群PS1/n)。磁性測量結果表明,Ca2+離子摻雜引起Co離子和Mn離子化合價的變化,并改變了 Co離子和Mn離子的超交換作用的種類以及不同磁性相的比例,導致樣品的居里溫度Tc和矯頑力HC降低,并增強了交換偏置效應。電性測量結果表明,所有樣品的導電機制均符合VRH模型,樣品電阻率隨Ca2+離子摻雜量的增加而減小。樣品均表現(xiàn)出自旋相關的負磁電阻效應,這種效應可用電阻網絡理論來解釋。在低溫下(T200K),少量的Ca2+離子摻雜(x≤0.2)可優(yōu)化多晶樣品中鐵磁相互作用和反鐵磁相互作用的比例,從而在一定程度上增強磁電阻效應。在105K、7T的條件下,樣品x = 0.2可增強負磁電阻效應接近10%,達到58%。這為研究La2CoMnO6的小半徑離子摻雜效應提供實驗依據(jù),也為增強鑭系錳基雙鈣鈦礦材料磁電阻效應的研究提供參考。2.La2CoMn06鈷位摻雜B (B = Fe、Cu)的磁性和電輸運性質的研究。用固相反應方法制備了多晶 La2Co1-xFexMnO6 (0≤x≤1.0)、La2Co1-xCuxMnO6 (0≤x≤0.5)。系統(tǒng)地研究了 Fe3+或Cu2+離子摻雜Co位對La2CoMnO6磁和電特性的影響。X射線衍射分析顯示,Fe3+或Cu2+離子摻雜樣品具有正交扭曲的雙鈣鈦礦結構(空間群Pbnm)。La2Co1-xBxMnO6的磁性測量結果表明,Fe3+或Cu2+離子摻雜均導致La2CoMn06的居里溫度Tc降低。Fe3+摻雜會降低La2CoMnO6的矯頑力Hc,當Co/Fe離子數(shù)比例達到1時,可獲得最大的交換偏置效應。少量Cu2+離子摻雜可有效調控La2CoMnO6的磁性,適量的Cu2+離子摻雜(x = 0.3)可有效提高其矯頑力Hc。電性測量結果表明,Fe3+或Cu2+離子摻雜可使樣品的導電機制由三維VRH模型逐漸轉變?yōu)門A模型。La2Co1-xBxMnO6(B = Fe、Cu)均表現(xiàn)出自旋相關的負磁電阻效應,Fe3+離子摻雜x≤0.1時,能增強低溫下(T150K)樣品的磁電阻效應;Cu2+離子摻雜量較低時(x≤0.1),磁電阻效應在低場下(H 5 T)得到增強。該結果可為進一步研究雙鈣鈦礦材料B位摻雜效應和通過B位離子摻雜調控該類材料的磁、電特性提供實驗依據(jù)。3.CH3NH3PbI3鉛位摻雜B(B = Mn/ (Mn和Co))的磁性研究。用蒸發(fā)溶劑法制備了 CH3NH3PbI3多晶樣品及摻雜樣品CH3NH3Pb1-xBxI3-2xCl2x。X射線衍射分析表明樣品均具有正交結構。樣品的磁性測量結果表明,磁性摻雜樣品在5K下均具有極弱的鐵磁性,Mn2+或Co2+離子之間的直接相互作用是該磁性產生的原因。在高摻雜量時,CH3NH3Pb0.34Mn0.33Co0.3311.68C11.32樣品中存在部分反鐵磁性并顯示出交換偏置效應。在摻雜離子總量x 一定時,單一Mn2+離子摻雜樣品的磁性強于Mn2+和Co2+離子共摻的磁性。該結果可為有機鈣鈦礦磁性摻雜方面的研究提供有力的實驗支持,也為探索新型磁性有機鈣鈦礦材料提供實驗依據(jù)。
[Abstract]:Perovskite-like compounds (e.g., double perovskite oxide La2CoMnO6, organic perovskite CH3NH3PbI3, etc.) have rich physical properties. La2CoMn06 has a high Curie temperature, a large magnetic resistance effect and a dielectric constant, and is widely researched and applied in the fields of magnetic and spin electronics and devices; and the CH3NH3PbI3 has excellent photovoltaic performance, and is a hot spot material for novel solar cell research. Ion doping is one of the important means to control the physical properties of the material, so the influence of the ion doping on the magnetic and electrical properties is discussed by doping the Pb in the La and Co bits in La2CoMnO6 and the Pb in the CH3NH3PbI3 with different ions. The crystal structure, surface morphology and magnetic and electrical transport properties of the samples were studied by means of X-ray diffractometer, scanning electron microscope and PPMS. The specific research results are as follows:1. Study on the properties of the magnetic and electrical transport of the La2CoMnO6 in-situ doped Ca. The effects of Ca 2 + ion doping on the crystal structure, surface morphology, magnetic properties, electrical property and magnetic resistance of La2CoMnO6 were studied by solid-phase reaction. The X-ray diffraction analysis shows that the La-site doped Ca2 + ions hold the monoclinic double perovskite structure of the crystal (PS1/ n in the space group). The magnetic measurement results show that the Ca 2 + ion doping results in the change of the valence of Co ion and Mn ions, and the type of the superexchange of Co and Mn ions and the proportion of different magnetic phases are changed, which leads to the reduction of the Curie temperature Tc and the coercive force HC of the sample. And the exchange bias effect is enhanced. The electrical measurement results show that the conductivity of all the samples is in accordance with the VRH model, and the resistivity of the sample decreases with the increase of the Ca 2 + ion doping. The samples show spin-dependent negative magnetic resistance effects, which can be explained by the resistance network theory. At low temperature (T200K), a small amount of Ca2 + ion doping (x-0.2) can optimize the ratio of the ferromagnetic interaction and the anti-ferromagnetic interaction in the polycrystalline sample, thereby enhancing the magnetic resistance effect to a certain extent. Under the conditions of 105K and 7T, the effect of x = 0.2 on the negative magnetic resistance is close to 10%, reaching 58%. This paper provides an experimental basis for the study of the effect of the small-radius ion doping of La2CoMnO6, and also provides a reference for the study of the magnetic resistance effect of the double perovskite material of the SiCoMnO6, and the magnetic and electric transport properties of the La2CoMn6 Co-position-doped B (B = Fe, Cu) are studied. Polycrystalline La2Co1-xFexMnO6 (0-x-1.0) and La2Co1-xCuxMnO6 (0-x-0.5) were prepared by solid-phase reaction. The effect of Fe 3 + or Cu 2 + on the magnetic and electrical properties of La2CoMnO6 was studied systematically. The X-ray diffraction analysis shows that the Fe3 + or Cu2 + ion-doped sample has an orthogonal twisted double perovskite structure (the space group Pbnm). The magnetic measurements of La2Co1-xBxMnO6 show that the Curie temperature Tc of La2CoMn06 is reduced by the doping of Fe3 + or Cu2 +. Fe3 + doping reduces the coercivity Hc of La2CoMnO6, and when the ratio of the number of Co/ Fe ions reaches 1, the maximum exchange bias effect can be obtained. A small amount of Cu2 + ion doping can effectively control the magnetic properties of La2CoMnO6, and a proper amount of Cu2 + ion doping (x = 0.3) can effectively improve the coercive force Hc. The electrical measurement results show that the conduction mechanism of the sample can be gradually changed into the TA model by the three-dimensional VRH model by the doping of the Fe3 + or Cu2 + ions. La2Co1-xBxMnO6 (B = Fe, Cu) show the spin-related negative magnetic resistance effect. When the Fe3 + ion is doped with x-0.1, the magnetic resistance effect of the (T150K) sample can be enhanced; when the amount of Cu2 + ion is lower (x = 0.1), the magnetic resistance effect is enhanced under the low field (H 5T). The results can provide an experimental basis for the further study of the B-position doping effect of the double perovskite material and the magnetic and electrical properties of the material through B-position ion doping. The samples of CH3NH3PbI3 and the doped samples of CH3NH3Pb1-xBxI3-2xCl2x were prepared by the evaporation solvent method. The X-ray diffraction analysis showed that the samples had the orthogonal structure. The magnetic measurements of the samples show that the magnetic doping samples have very weak ferromagnetism at 5K, and the direct interaction between Mn2 + or Co2 + ions is the cause of the magnetic production. At the time of high doping, some antiferromagnetism in the samples of CH3NH3Pb0. 34Mn0.33Co0. 3311.68C11.32 and the exchange bias effect were shown. The magnetic properties of a single Mn2 + ion-doped sample are stronger than that of Mn2 + and Co2 + ions when the total amount of the doping ions x is constant. The result can provide a powerful experimental support for the research of the magnetic doping of the organic perovskite, and also provides the experimental basis for exploring the new type of magnetic organic perovskite material.
【學位授予單位】：東南大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O611.3
本文編號：2506755
[Abstract]:Perovskite-like compounds (e.g., double perovskite oxide La2CoMnO6, organic perovskite CH3NH3PbI3, etc.) have rich physical properties. La2CoMn06 has a high Curie temperature, a large magnetic resistance effect and a dielectric constant, and is widely researched and applied in the fields of magnetic and spin electronics and devices; and the CH3NH3PbI3 has excellent photovoltaic performance, and is a hot spot material for novel solar cell research. Ion doping is one of the important means to control the physical properties of the material, so the influence of the ion doping on the magnetic and electrical properties is discussed by doping the Pb in the La and Co bits in La2CoMnO6 and the Pb in the CH3NH3PbI3 with different ions. The crystal structure, surface morphology and magnetic and electrical transport properties of the samples were studied by means of X-ray diffractometer, scanning electron microscope and PPMS. The specific research results are as follows:1. Study on the properties of the magnetic and electrical transport of the La2CoMnO6 in-situ doped Ca. The effects of Ca 2 + ion doping on the crystal structure, surface morphology, magnetic properties, electrical property and magnetic resistance of La2CoMnO6 were studied by solid-phase reaction. The X-ray diffraction analysis shows that the La-site doped Ca2 + ions hold the monoclinic double perovskite structure of the crystal (PS1/ n in the space group). The magnetic measurement results show that the Ca 2 + ion doping results in the change of the valence of Co ion and Mn ions, and the type of the superexchange of Co and Mn ions and the proportion of different magnetic phases are changed, which leads to the reduction of the Curie temperature Tc and the coercive force HC of the sample. And the exchange bias effect is enhanced. The electrical measurement results show that the conductivity of all the samples is in accordance with the VRH model, and the resistivity of the sample decreases with the increase of the Ca 2 + ion doping. The samples show spin-dependent negative magnetic resistance effects, which can be explained by the resistance network theory. At low temperature (T200K), a small amount of Ca2 + ion doping (x-0.2) can optimize the ratio of the ferromagnetic interaction and the anti-ferromagnetic interaction in the polycrystalline sample, thereby enhancing the magnetic resistance effect to a certain extent. Under the conditions of 105K and 7T, the effect of x = 0.2 on the negative magnetic resistance is close to 10%, reaching 58%. This paper provides an experimental basis for the study of the effect of the small-radius ion doping of La2CoMnO6, and also provides a reference for the study of the magnetic resistance effect of the double perovskite material of the SiCoMnO6, and the magnetic and electric transport properties of the La2CoMn6 Co-position-doped B (B = Fe, Cu) are studied. Polycrystalline La2Co1-xFexMnO6 (0-x-1.0) and La2Co1-xCuxMnO6 (0-x-0.5) were prepared by solid-phase reaction. The effect of Fe 3 + or Cu 2 + on the magnetic and electrical properties of La2CoMnO6 was studied systematically. The X-ray diffraction analysis shows that the Fe3 + or Cu2 + ion-doped sample has an orthogonal twisted double perovskite structure (the space group Pbnm). The magnetic measurements of La2Co1-xBxMnO6 show that the Curie temperature Tc of La2CoMn06 is reduced by the doping of Fe3 + or Cu2 +. Fe3 + doping reduces the coercivity Hc of La2CoMnO6, and when the ratio of the number of Co/ Fe ions reaches 1, the maximum exchange bias effect can be obtained. A small amount of Cu2 + ion doping can effectively control the magnetic properties of La2CoMnO6, and a proper amount of Cu2 + ion doping (x = 0.3) can effectively improve the coercive force Hc. The electrical measurement results show that the conduction mechanism of the sample can be gradually changed into the TA model by the three-dimensional VRH model by the doping of the Fe3 + or Cu2 + ions. La2Co1-xBxMnO6 (B = Fe, Cu) show the spin-related negative magnetic resistance effect. When the Fe3 + ion is doped with x-0.1, the magnetic resistance effect of the (T150K) sample can be enhanced; when the amount of Cu2 + ion is lower (x = 0.1), the magnetic resistance effect is enhanced under the low field (H 5T). The results can provide an experimental basis for the further study of the B-position doping effect of the double perovskite material and the magnetic and electrical properties of the material through B-position ion doping. The samples of CH3NH3PbI3 and the doped samples of CH3NH3Pb1-xBxI3-2xCl2x were prepared by the evaporation solvent method. The X-ray diffraction analysis showed that the samples had the orthogonal structure. The magnetic measurements of the samples show that the magnetic doping samples have very weak ferromagnetism at 5K, and the direct interaction between Mn2 + or Co2 + ions is the cause of the magnetic production. At the time of high doping, some antiferromagnetism in the samples of CH3NH3Pb0. 34Mn0.33Co0. 3311.68C11.32 and the exchange bias effect were shown. The magnetic properties of a single Mn2 + ion-doped sample are stronger than that of Mn2 + and Co2 + ions when the total amount of the doping ions x is constant. The result can provide a powerful experimental support for the research of the magnetic doping of the organic perovskite, and also provides the experimental basis for exploring the new type of magnetic organic perovskite material.
【學位授予單位】：東南大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O611.3
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