掺杂钙钛矿结构化合物的磁性和电输运性质
发布时间：2019-06-27 11:39
【摘要】：钙钛矿类化合物(例如双钙钛矿氧化物La2CoMnO6、有机钙钛矿CH3NH3PbI3等)具有丰富的物理特性。La2CoMn06具有较高的居里温度、较大的磁电阻效应和介电常数·等,在磁学与自旋电子学及器件领域有广泛研究与应用;CH3NH3PbI3具有优良的光伏性能,是新型太阳能电池研究的热点材料。离子掺杂是有效调控材料物理特性的重要手段之一,因此本论文用不同离子对La2CoMnO6中La位和Co位以及CH3NH3PbI3中Pb位进行掺杂,探讨了离子掺杂对磁性与电性的影响机制。通过X射线衍射仪、扫描电子显微镜、PPMS等设备对样品的晶体结构、表面形貌以及磁性和电输运特性等进行了系统的研究。具体研究成果如下:1. La2CoMnO6镧位掺杂Ca的磁性和电输运性质的研究。用固相反应方法制备了多晶La2.xCaxCoMn06 (0≤x≤0.5)样品,系统研究了 Ca2+离子掺杂对La2CoMnO6晶体结构、表面形貌、磁性、电性和磁电阻效应的影响。X射线衍射分析表明La位掺杂Ca2+离子保持了晶体单斜双钙钛矿结构(空间群PS1/n)。磁性测量结果表明,Ca2+离子掺杂引起Co离子和Mn离子化合价的变化,并改变了 Co离子和Mn离子的超交换作用的种类以及不同磁性相的比例,导致样品的居里温度Tc和矫顽力HC降低,并增强了交换偏置效应。电性测量结果表明,所有样品的导电机制均符合VRH模型,样品电阻率随Ca2+离子掺杂量的增加而减小。样品均表现出自旋相关的负磁电阻效应,这种效应可用电阻网络理论来解释。在低温下(T200K),少量的Ca2+离子掺杂(x≤0.2)可优化多晶样品中铁磁相互作用和反铁磁相互作用的比例,从而在一定程度上增强磁电阻效应。在105K、7T的条件下,样品x = 0.2可增强负磁电阻效应接近10%,达到58%。这为研究La2CoMnO6的小半径离子掺杂效应提供实验依据,也为增强镧系锰基双钙钛矿材料磁电阻效应的研究提供参考。2.La2CoMn06钴位掺杂B (B = Fe、Cu)的磁性和电输运性质的研究。用固相反应方法制备了多晶 La2Co1-xFexMnO6 (0≤x≤1.0)、La2Co1-xCuxMnO6 (0≤x≤0.5)。系统地研究了 Fe3+或Cu2+离子掺杂Co位对La2CoMnO6磁和电特性的影响。X射线衍射分析显示,Fe3+或Cu2+离子掺杂样品具有正交扭曲的双钙钛矿结构(空间群Pbnm)。La2Co1-xBxMnO6的磁性测量结果表明,Fe3+或Cu2+离子掺杂均导致La2CoMn06的居里温度Tc降低。Fe3+掺杂会降低La2CoMnO6的矫顽力Hc,当Co/Fe离子数比例达到1时,可获得最大的交换偏置效应。少量Cu2+离子掺杂可有效调控La2CoMnO6的磁性,适量的Cu2+离子掺杂(x = 0.3)可有效提高其矫顽力Hc。电性测量结果表明,Fe3+或Cu2+离子掺杂可使样品的导电机制由三维VRH模型逐渐转变为TA模型。La2Co1-xBxMnO6(B = Fe、Cu)均表现出自旋相关的负磁电阻效应,Fe3+离子掺杂x≤0.1时,能增强低温下(T150K)样品的磁电阻效应;Cu2+离子掺杂量较低时(x≤0.1),磁电阻效应在低场下(H 5 T)得到增强。该结果可为进一步研究双钙钛矿材料B位掺杂效应和通过B位离子掺杂调控该类材料的磁、电特性提供实验依据。3.CH3NH3PbI3铅位掺杂B(B = Mn/ (Mn和Co))的磁性研究。用蒸发溶剂法制备了 CH3NH3PbI3多晶样品及掺杂样品CH3NH3Pb1-xBxI3-2xCl2x。X射线衍射分析表明样品均具有正交结构。样品的磁性测量结果表明,磁性掺杂样品在5K下均具有极弱的铁磁性,Mn2+或Co2+离子之间的直接相互作用是该磁性产生的原因。在高掺杂量时,CH3NH3Pb0.34Mn0.33Co0.3311.68C11.32样品中存在部分反铁磁性并显示出交换偏置效应。在掺杂离子总量x 一定时,单一Mn2+离子掺杂样品的磁性强于Mn2+和Co2+离子共掺的磁性。该结果可为有机钙钛矿磁性掺杂方面的研究提供有力的实验支持,也为探索新型磁性有机钙钛矿材料提供实验依据。
[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.
【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O611.3
本文编号：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.
【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O611.3
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