"Neutron Scattering, Transport, and Dilatometry Measurements of Magnetic Materials"

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A very large fraction of our modern technology is based on materials and their properties, e.g., microprocessors, computer hard drives, light-emitting diodes. These materials allow for cost-effective, reliable devices. The useful properties are often based on some fundamental physics in the system. In the case of computer hard drives, a very small part of the drive acts as a permanent magnet, whose polarity can be switched by a write head and measured by a read head at extremely high speeds. The proposed research focuses on magnetic materials, that order in a large number of ways, often in a way that is more exotic than the computer hard drive. In these cases, we are still trying to figure out the details of the ordering and how it comes about. Understanding the magnetism in these systems is the primary goal of this research. This is important from a fundamental viewpoint, but also for possible applications. In many cases, these systems can undergo large changes of ordering with very small changes in temperature, magnetic field, or by adding dopants. In one of the materials, the magnetism can almost disappear by forming pairs of oppositely aligned magnets. In another, a change in magnetism makes a big change in the electrical conductivity, like a magnetic switch. Another material has a spiral type of order that is related to materials that do not have any electrical resistance. The research involves neutron scattering, which gives a lot of information about magnetism on an atom by atom or electron by electron scale, but is carried out at very large facilities. There are also measurements of the electrical resistance and direct measurements of sample expansion using sensitive equipment.