Correlated magnets and superconductors explored using muon-spin rotation

植入的μ子给量子材料提供了一个独特的局部视角。通过测量注入的μ子自旋在局部磁场中的旋转，这反过来又是由附近磁矩产生的偶极场引起的，人们可以遵循作为温度函数的磁序参数。如果有一系列的μ介子位点，该技术可以提供有关内部磁场分布的信息。即使在磁转变温度以上，测量到的μ子自旋弛豫也可以提供有关磁涨落和自旋动力学的信息。在超导体中，这项技术特别有价值，因为测量的内部场分布可以让我们推断出配对机制。然而，有一个基本的限制，这是来自于缺乏知识的μ子的植入部位和μ子的扰动其主机的不确定性。我们已经发现，这个问题可以解决使用电子结构计算，使用我们已经开发的技术，我们称之为“DFT+ μ”，密度泛函理论与包括μ子。这个D. Phil该项目将涉及在新磁体和超导体上使用μ子的实验，以及由DFT+ μ方法激发的研究。其目的是进一步了解磁性和超导材料，但也通过获得新的见解μ子网站的性质，以扩展μ子自旋旋转技术。

Implanted muons give a unique local perspective on quantum materials. By measuring the rotation of the implanted muon spin in the local magnetic field, which in turn results from the dipolar field arising from nearby magnetic moments, one can follow the magnetic order parameter as a function of temperature. If there are a range of muon sites the technique can provide information about the internal magnetic field distribution. Even above the magnetic transition temperature, the measured relaxation of the muon spin can provide information about magnetic fluctuations and spin dynamics. In superconductors the technique is particularly valuable because the measured internal field distribution can allow us to infer the pairing mechanism. However, there is a fundamental limitation of this technique which comes from the lack of knowledge of the implantation site of the muon and the uncertainty about the muon's perturbation of its host. We have found that this problem can be addressed using electronic-structure calculations using a technique we have developed which we call "DFT+mu", density functional theory with an included muon. This D.Phil. project will involve experiments using muons on new magnets and superconductors, as well as investigations motivated by the DFT+mu method. The aim is to further our understanding of the magnetic and superconducting materials, but also to extend the muon-spin rotation technique by gaining new insights into the nature of muon sites.