The variable contexts of Fremont habitation sites in Utah Valley often make identification of those sites very challenging for archaeologists. Pit houses and other structures throughout the valley are frequently in plowed fields or other disturbed contexts that obscure their more exact location and nature. The application of geophysical technologies at archaeological sites throughout the world, including in North America, has proven to be an effective means of subsurface archaeological survey. However, geophysical techniques have been underutilized in Fremont archaeology. This paper reports on the employment of two geophysical methods, ground-penetrating radar (GPR) and fluxgate gradiometer surveys, at three known Fremont habitation sites in southern Utah Valley – the Wolf Village, Wolf Mound, and Snow Farm sites. The preliminary geophysical surveys and later ground-truthing of various geophysical anomalies reveals the effectiveness of these methods in identifying where architectural or other cultural features exist below the surface.

Les films magnétiques ultra-minces font partie intégrante des technologies d'aujourd'hui, comme l'illustre leur omniprésence dans de nombreuses applications courantes telles que les disques durs. A cause de leurs dimensions réduites, les propriétés magnétiques spécifiques à ces échelles conduisent à la formation de structures de spin exotiques et de taille nanométrique. Pour explorer ces matériaux en détail, nous utilisons un magnétomètre à balayage développé dans notre laboratoire et qui est basé sur un défaut de spin unique dans le diamant. Ce capteur non-invasif peut mesurer à l'échelle nanométrique à la fois le champ magnétique et la topographie, et fonctionne aux conditions ambiantes. En développant une méthode d'évaluation originale du champ magnétique, nous déterminons la structure interne de parois de domaines ferromagnétiques et quantifions la force de l'interaction Dzyaloshinskii-Moriya dans des hétérostructures à couches minces. Ensuite, nous mettons en évidence le rôle clé du désordre et de l'histoire magnétique sur la stabilisation des skyrmions dans un échantillon de bicouche magnétique. Enfin, nous visualisons dans l'espace réel une spirale de spin de 70 nm de période dans le matériau multiferroïque BiFeO3 et nous manipulons sa direction de propagation avec des champs électriques. Les connaissances tirées de ces études aideront à exploiter au maximum les capacités des matériaux magnétiques à couche ultra-mince et à les mettre en œuvre dans de nouveaux dispositifs de spintronique. / Thin film magnetic materials are an integral part of today’s technology and widespread applications like the magnetic hard drive disk mirror their potential. Due to their reduced dimensions, size-specific magnetic properties induce the formation of nanoscale, exotic spin structures. To explore such materials in detail, we utilize a home-built nitrogen vacancy scanning magnetometer, based on a single defect in diamond. This non-perturbative probe combines nanoscale magnetic field- and spatial resolution and works under ambient conditions. We develop a new way to determine the inner structure of magnetic domain walls and quantify the strength of the Dzyaloshinskii-Moriya interaction in thin film heterostructures. We reveal the key role of disorder and magnetic history on the stabilization of skyrmions in a magnetic bilayer sample. Finally, we reveal the 70nm-pitch spin spiral in the multiferroic bismuth ferrite in real space and manipulate its propagation direction with electric fields. The insight gained from these studies will help to exploit the full capacity of thin film magnetic materials for spintronic application.

Cette thèse vise à étudier l'interaction résonante d'un rayonnement laser avec une couche mince d'épaisseur sub-longueur d'onde de vapeur alcaline atomique confinée en nanocellule ; et les applications de détection qui en émergent.Nous nous concentrons sur la réflexion sélective se produisant à l'interface entre une fenêtre diélectrique et une vapeur résonante, et montrons que la dérivée des spectres de réflexion sélective est composée de résonances étroites dont les maxima correspondent aux positions des transitions atomiques. Ces résonances sont observées avec une largeur spectrale jusqu'à quinze fois plus fine que la largeur Doppler du milieu, et leurs amplitudes évoluent de façon linéaire avec celles des transitions. Grâce à ces propriétés et aux faibles épaisseurs de cellule pouvant être sondées, nous examinons les interactions atome-surface et mesurons le coefficient C3 de l'interaction de van der Waals.Nous présentons un modèle théorique décrivant l'interaction entre lumière quasi-résonante et nanocellule remplie d'une vapeur alcaline sous champ magnétique statique. Ce modèle se montre en excellent accord avec les résultats expérimentaux pour une large gamme de champs magnétiques depuis le régime Zeeman jusqu'au régime Paschen-Back. Au vu de ces résultats, nous proposons un concept de magnétomètre optique basé sur les nanocellules. Une preuve de faisabilité est présentée et une analyse en performance révèle un coefficient de variation des mesures de champs magnétiques inférieur à 5 % dans la gamme 0,4 - 2 kG. / This thesis is aimed at studying the resonant interaction of a laser radiation with an atomic alkali vapor layer of wavelength-scale thickness confined in an optical nanocell; and emerging sensing applications.We focus our attention on the selective reflection arising at the interface between a dielectric window and a resonant alkali vapor, and show that the derivative of selective reflection spectra exhibit narrow resonances whose maxima are located exactly at atomic resonance frequencies. These resonances are observed with a spectral linewidth up to fifteen times smaller than the Doppler linewidth of the medium and their amplitudes scale linearly with respect to the transitions ones. Owing to these properties and the possibility to probe thin atomic layers, we investigate atom-surface interaction and measure the C3 coefficient of the van der Waals interaction.We present a theoretical model describing the interaction of near-resonant laser light with alkali vapor-filled nanocell in the presence of an external static magnetic field. We show an excellent agreement between recorded and calculated spectra in a wide range of magnetic fields spanning from Zeeman to Paschen-Back regimes. Following these results, we propose a concept for a nanocell-based optical magnetometer. A proof of feasibility is presented and a performance analysis reveals a coefficient of variation for the magnetic field measurements less than 5% in the range 0.4 - 2 kG.

Astrophysical observations indicate the existence of dark matter through its gravitational interaction, but since its other interactions remain undetected, its particle nature is still unknown. There are several dark matter candidates, one being a hypothetical particle called axion that can have three types of non-gravitational couplings: electromagnetic, electric dipole moment (EDM), and gradient. This dissertation presents experimental approaches and axionlike dark matter search results from two table-top experiments: Cosmic Axion Spin Precession Experiment (CASPEr-electric) sensitive to EDM and gradient couplings, and Search for Halo Axions with Ferromagnetic Toroids (SHAFT) sensitive to electromagnetic coupling. CASPEr-electric is a resonant search for axionlike dark matter through the induced nuclear spin precession. The experimental approach is measuring nuclear magnetic resonance (NMR) of the heavy atom in a ferroelectric crystal. Experimental setup is characterized using pulsed NMR calibration measurements. Recorded search data that is sensitive to axionlike dark matter is analyzed by optimal filtering and then setting a detection threshold based on the histogram of power spectral density modeled as a Gaussian distribution. The candidates above the threshold are all rejected through statistical fluctuations and scan/re-scan measurements. CASPEr-electric places the upper bounds on the EDM and gradient couplings of axionlike dark matter in the Compton frequency range from 39.1 MHz to 40.2 MHz. SHAFT is a broadband search for axionlike dark matter through the induced oscillatory magnetic field. The resultant magnetic flux is measured with a precision magnetometer called superconducting quantum interference device (SQUID), coupled to a coil placed on the inner surface of a ferromagnetic toroid. After analyzing the search data, all candidates are rejected and SHAFT places a limit on electromagnetic coupling of axionlike dark matter between 3 kHz and 3 MHz Compton frequencies. Finally, coupling limits placed by CASPEr-electric and SHAFT are evaluated in the wider parameter space, and possible future directions that both experiments could take to improve their sensitivities to axionlike dark matter are discussed. / 2022-09-27T00:00:00Z

No description available.

Ground-penetrating radar (GPR) and magnetometry were used at Tel Shimron, an archaeological site in Israel’s Jezreel Valley. GPR primarily measures electric properties while magnetometry measures magnetic properties, making them complementary methods for subsurface prospection. Magnetometry can be collected and processed quickly, making it an ideal landscape-scale reconnaissance tool. It takes more time to collect, process, and interpret GPR data, but the result is a higher resolution dataset. In addition, GPR often works better than magnetometry in desert environments such as the Jezreel Valley. Conventional wisdom suggests that GPR should not be used as a landscape-scale reconnaissance tool unless there is ample time to process and interpret the data. Despite this, GPR was used at Tel Shimron with standardized, semi-automated processing routines and eight field technicians to produce an end product. The GPR survey revealed more about the subsurface than magnetometry, including three potential dwellings and a Bronze Age city gate.

Electromagnetic induction (EM) methods have been utilised in a recent surge of archaeological applications across continental Europe, Ireland and Scandinavia. Development of multi-exploration depth instruments and improvements to instrument stability have improved its reputation as an effective method for mapping archaeological remains. Despite these advances, EM methods are comparatively lacking in rigour when for British sites. Through a structured scheme of experimental analysis and fieldwork, this thesis develops an understanding of the responses of EM instruments over a range of British archaeology, including earthworks, field systems, burials, modern remains, and a Cistercian abbey; the results of which demonstrate its effective over a diversity of environments. The impact of instrument-based issues on the collected measurements was quantified through a scheme of experiments targeting instrument drift, calibration and elevation. Dedicated instrument operation and processing workflows were developed based on the collective field and experimental results, which recommend best practice guidelines for improving the quality and accuracy of collected data. The link between instrument measurements and buried archaeology was further developed through a structured analysis of the EM datasets with complementary earth resistance and magnetic results. The integration of the EM, earth resistance and magnetic datasets was utilised to develop an enhanced archaeological characterisation of subsurface features. While the earth resistance and magnetic methods generally responded to different aspects of the buried archaeology, the EM surveys were able to detect a range of responses evident in the results of the former methods. Therefore, the role of EM methods within this characterisation are shown to “bridge the gap” between the earth resistance and magnetic methods, while providing a comprehensive characterisation of the remains in their own right. / The supplementary material files from Appendix 2 are not available online.

This thesis presents experimental results on strongly interacting γ-Fe2O3 magnetic nanoparticles and their collective properties. The main findings are that very dense randomly packed (≈60%) γ-Fe2O3 nanoparticles form a replica of a spin glass. The magnetic properties of the nanoparticle system are in most regards the same as those of an atomic spin glass. The system is therefore proposed as a model superspin glass. In superspin glasses the interacting building blocks that form the collective state are single domain nanoparticles, superspins with a magnetic moment of about 10000 μB, which can be compared to the atomic magnetic moment in spin glasses of approximately 1 μB.  It was found that the relaxation time of the individual nanoparticles impacts the collective properties and governs the superspin dimensionality. Several dense compacts, each prepared with nanoparticles of a specific size, with diameters 6, 8, 9 and 11.5 nm, were studied. All the studied compacts were found to form a superspin glass state. Non-interacting reference samples, consisting of the same particles but coated with a silica shell, were synthesized to determine the single particle magnetic properties.  It was also found that the effects of the nanoparticle size distribution, which lead to a variation of the magnetic properties, can be mitigated by having strong enough interparticle interactions. The majority of the work was carried out using SQUID magnetometry.

The aim of the thesis is the identification and characterization of soils with andic properties using the magnetic methods. Investigated soil is located in the Velký Roudný in the Nízký Jeseník mountain. This is the only known area with Andosols on the territory of the Czech Republic. Magnetic measurements will be performed both in the field and in the laboratory, and will be accomplished by geochemical analyses necessary for accurate pedological characterisation. Magnetic data will be interpreted in termagnetická susceptibilita of the geological and environmental conditions. The results will be compared with the properties of the Andosols from the French Massif Central.

Layered crystals with magnetic elements as Co and Fe have been studied. In TlCo2Se2, where Co atoms in one sheet are separated by Tl and Se from the next Co sheet, magnetic interaction within and between the sheets have been studied. Samples doped with 4% 57Fe replaced Co, show a magnetic spiral character with hyperfine fields in a flower shape in the ab-plane. The magnetic moment of 0.46 μB per Co atom derived from the average field is in good agreement with the result from neutron diffraction. In TlCu1.73Fe0.27Se2 the easy axis of magnetisation is the c-axis. The magnetic moment calculated from the Mössbauer data and SQUID magnetrometry is 0.97 μB per Fe atom with TC = 55(5) K. Multilayers of different elements have been studied. The effect of vanadium atoms on iron atoms at the interface of FeNi/V multilayers has been determined and the intermixing at the interface has been calculated to be 2-3 monolayers. For FeNi/Co 1/1 monolayer the magnetic hyperfine field (Bhf) is 45° out-of-plane, while for superlattices containing 2 to 5 monolayers it is in the plane. An study on Fe/Co superlattice were done by experimental, theoretical and simulational methods. The Bhf is highest for the Fe at the second layer next to the interface and gets the bulk value in the centre of thicker Fe layers. Studied magnetic nanoparticles coated with a lipid bilayer (magnetoliposomes) are found to have the magnetite structure but being non-stoichiometric as a result of the manufacturing process. The composition was approximately 32% γ-Fe2O3 and 68% Fe3O4. The oxidation evolution and its effect on magnetic properties of Fe clusters were also studied by means of different techniques. The extraction and insertion mechanism of lithium in the cathode material Li2FeSiO4 has been monitored by in situ x-ray diffraction and Mössbauer spectroscopy during the first two cycles. The relative amount of Fe+3/ Fe+2 at each end state was in good agreement with the results obtained from electrochemical measurements. A possible explanation to the observed lowering of the potential plateau from 3.10 to 2.80 V occurring during the first cycle, involves a structural rearrangement process in which some of the Li ions and the Fe ions are interchanged. The behaviour of small amounts of Fe in brass is investigated using Mössbauer spectroscopy. It was shown that a heat treatment can increase the amount of the precipitates of γ-Fe and ~650° C is the optimal treatment for having the highest amount of this phase.