Добірка наукової літератури з теми "Optical Atomic Magnetometry, Ultra-Low-Field NMR, Ultra-Low-Field MRI"

In this work, magneto-optical garnets were grown monolithically by low-temperature reactive RF sputtering, followed by an ultra-short (< 15sec) anneal. It was found that in addition to low thermal budgets due to timing, the temperature required (< 750°C) for garnet crystallization was also reduced compared to standard tube furnace annealing (> 1000°C). MgO and fused quartz were used as substrates because they will be useful for future buffer layers and optical claddings. Y-Fe-O films were made with systematically varied compositions and the chemical, structural, and optical properties of the resulting films were analyzed. A solid solution single phase field for YIG was found that spanned a wide range of compositions (30.1 ∼ 49.0 atomic % of Fe). The resulting YIG quality was measured by vibrating sample magnetometry (VSM), X-ray diffraction (XRD), and measurements of Faraday rotation (FR). Although the XRD results showed that the films had isotropic crystallinity, the VSM indicated that shape anisotropy dominated the magnetic properties. Out of plane FR measurements yielded up to 0.2°/μm at 632nm rotations. This rotation will be higher in plane. All of these tests demonstrated that the YIG was comparable to YIG grown by standard annealing and also by in-situ crystallization.

In this thesis the candidate proposes some technical and fundamental advances for NMR and MRI measurements in the ultra-low field (ULF) regime executed with optical-atomic-magnetometers (OAMs). This regime corresponds to field intensities such to make the nuclei precess at frequencies as low as tens/hundreds Hz. A self-optimized compensation system reduces the magnetic disturbances so to make the magnetometer suited to detect those ULF signals in an unshielded environment. The magnetometer is exploited as a high-sensitivity non-inductive sensor for ULF-NMR signal detection. Besides application in ULF-NMR spectroscopy, the simultaneous analysis of nuclear and atomic precession is used in a novel hybrid setup, which enables the detection of diluted magnetic contaminants. As predominant result an inhomogeneous-magnetic-dressing based (IDEA) technique has been devised enabling the first in-situ ULF-MRI detection by OAMs with sub-millimetric resolution.