铬基、锰基超导体探索及物性研究

发布时间：2018-03-27 07:31

  本文选题：Cr基超导　切入点：Mn基超导　出处：《陕西师范大学》2015年硕士论文

【摘要】：最近发现的高压下CrAs和MnP的超导电性,使CrAs和MnP分别成为Cr基和Mn基第一个超导体化合物,这一发现在超导领域引起了巨大的反响。CrAs和MnP的体超导电性出现在一个反铁磁量子临界点附近,暗示了非常规的超导配对机制。然而很多揭示超导微观机制的实验手段很难在高压下进行。因此尝试用化学掺杂的方法探索两个体系中更多可能的超导电性,实现Cr基和Mn基化合物的常压超导,对研究CrAs和MnP的非常规超导电性非常重要。本文的研究工作在此基础上展开。本文首次利用助熔剂法成功制备出掺杂的CrAs和MnP0.8B0.2单晶样品,并对CrAs1-xPx和MnP0.8B0.2单晶样品进行了系统的低温物性研究,最后与CrAs和MnP高压下的实验结果进行比较。本文主要由以下三部分构成：第一部分首先介绍了CrAs单晶的基本物性和高压下CrAs的超导电性。随后首次报道了CrAs1-xPx单晶样品的电阻率和比热实验数据。低温下正常态电阻率和电子比热系数γ的行为,说明在临界掺杂量x=0.05附近存在一个量子临界点,此时CrAs的长程磁有序已被完全压制掉。这与CrAs高压下的行为相似。但在2K以上没有观测到超导。第二部分首先介绍了高压诱导的MnP超导电性。随后首次报道了MnP0.8B0.2单晶样品的电阻率、比热和磁化率数据。Mn0.8B0.2单晶样品的磁矩很小,表现出强的磁各向异性。在低温下,MnP0.8B0.2中存在很强的磁阻效应。MnP0.8B0.2在100K以下处于倾斜反铁磁态或螺旋磁有序态。MnP0.8B0.2的低温正常态电阻率与MnP加压4-6GPa时的行为非常相似。德拜温度和MnP基本一样,而态密度相比MnP有明显增加。第三部分总结目前所做的工作,提出未解决的问题和未来的可行性研究方向。
[Abstract]:The recently discovered superconductivity of CrAs and MnP at high pressure makes CrAs and MnP the first superconductor compounds based on Cr and mn respectively. This discovery has caused great repercussions in the field of superconductivity. CRAs and MnP's bulk superconductivity appears near an antiferromagnetic quantum critical point. However, many experimental methods to reveal the microcosmic mechanism of superconductivity are difficult to carry out at high pressure. Therefore, we try to explore more possible superconductivities in the two systems by chemical doping. The realization of atmospheric superconductivity of Cr-based and Mn-based compounds is very important for the study of the unconventional superconductivity of CrAs and MnP. Based on this work, the doped CrAs and MnP0.8B0.2 single crystal samples were successfully prepared by flux method for the first time in this paper. The low temperature physical properties of CrAs1-xPx and MnP0.8B0.2 single crystal samples were studied systematically. In the first part, the basic physical properties of CrAs single crystal and the superconductivity of CrAs at high pressure are introduced, and then the CrAs1-xPx single crystal is reported for the first time. Experimental data on resistivity and specific heat of samples. Behavior of electrical resistivity and electron specific heat coefficient 纬 in normal state at low temperature. It is shown that there is a quantum critical point near the critical doping amount x0. 05. At this time, the long range magnetic order of CrAs has been completely suppressed. This is similar to the behavior of CrAs at high pressure. However, no superconductivity has been observed above 2K. In the second part, the superconductivity of MnP induced by high pressure is first introduced. Then MnP0.8B0.2 is reported for the first time. Resistivity of single crystal sample, The specific heat and magnetic susceptibility data. Mn0.8B0.2 single crystal sample has very small magnetic moment, The magnetoresistive effect of MnP0.8B0.2 is very strong at low temperature. The resistivity of MnP0.8B0.2 in the tilted antiferromagnetic state or spiral magnetically ordered state. MNP 0.8B 0.2 is very similar to the behavior of MnP pressurized 4-6GPa at low temperature. Debye temperature is basically the same as MnP, The density of states is much higher than that of MnP. The third part summarizes the work done at present and puts forward the unsolved problems and the future feasibility research direction.
【学位授予单位】：陕西师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM26

【共引文献】

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