| Popis: |
The idea that the spin degree of freedom of particles can be used to store and transport information has revolutionized the data storage industry and inspired a huge amount of research activity. Spin electronics, or spintronics, provides a plethora of potential improvements to conventional charge electronics that include increased functionality and energy efficiency.Scientists studying spintronics will need a multitude of characterization tools to sensitively detect spins in new materials and devices. There are already a handful of powerful techniques to image spin-related phenomena, but each has limitations. Magnetic resonance force microscopy, for example, offers sensitive detection of spin moments that are localized or nearly so but requires a high vacuum, cryogenic environment. Magnetometry based on nitrogen vacancy centers in diamond is a powerful approach, but requires the nitrogen vacancy center to be in very close contact to the spin system being studied to be able to measure the field generated by the system. Spin-polarized scanning tunneling microscopy provides perhaps the best demonstrated spatial resolution, but typically requires ultrahigh vacuum conditions and is limited to studying the surface of a sample. Traditional optical techniques such as Faraday or Kerr microscopy are limited in spatial resolution by the optical diffraction limit.In this dissertation I will present three new techniques we have developed to address some of these issues and to provide the community with new tools to help push forward spintronics and magnetism related research. I will start by presenting the first experimental demonstration of scanned spin-precession microscopy. This technique has the potential to turn any spin-sensitive detection technique into an imaging platform by providing the groundwork for incorporating a magnetic field gradient with that technique, akin to magnetic resonance imaging, and the mathematical tools to analyze the data and extract the local spin information. This use of magnetic field gradients also allows for imaging below the diffraction limit, even with optical techniques, and for subsurface imaging.Second, the technique of solid-state Hanle magnetometry will be presented. This is a novel technique for mapping the vector components of a magnetic field. We use the same measurement protocol as for a traditional Hanle type measurement, but we provide the framework for extracting the local magnetic field experienced by the spins being measured. The magnitude of the three vector components of the local field can be extracted by analyzing the lineshape of the Hanle type measurement, and the direction of one of the components can be extracted. We demonstrate this technique by measuring optically pumped spins in GaAs in the presence of a magnetic field from macroscopic permanent magnets and a micromagnetic particle.Finally, I will show how we have discovered a new effect using nitrogen vacancy (NV) centers in diamond which can be used to locally detect magnetization dynamics in adjacent magnetic materials. This effect occurs far from the NV centers' own magnetic resonance, but provides us with sensitive detection of magnetization dynamics, such as ferromagnetic resonance, spin wave modes or domain dynamics, even hundreds of nanometers away from the NV centers. The technique works at room temperature in ambient conditions and has the potential to allow for the imaging of ferromagnetic phenomena and spin transport at the nanoscale. |
