A system suitable for studying interactions between ⁸⁷Rb Rydberg atoms and metal surfaces has been constructed. This thesis describes the design and construction of the apparatus, and some test results. Atoms in a vapor cell magneto-optical trap are transferred to a macroscopic Ioffe-Pritchard trap, where they will be RF evaporatively cooled and loaded into a magnetic microtrap (atom chip). Confinement of cold clouds at controllable distances (5–200 μm)} from a metal surface is possible. The effects of atom-surface interactions can be studied with Rydberg atom spectroscopy. Some functionality of the apparatus has been demonstrated. Approximately 1.5×10⁷ atoms were loaded into a mirror MOT, and about 6×10⁶ atoms were optically pumped to the |F=2, m_F=2> hyperfine ground state and confined in a macroscopic Ioffe-Pritchard trap. The temperature of the cloud in the trap was 42 ± 5 μK, and the 1/e lifetime is 1–1.5 s. Forced RF evaporation has been used to measure the magnetic field at the trap minimum, but RF evaporative cooling has not yet been demonstrated.

In this thesis, we have performed systematical study of the complex impedance spectra(CIS) with the manganeses oxide thin films by the equivalent circuit model(ECM) composed of resistance and capacitance. The ECM has been utilized in analog of the electrical and dielectric properties of the granular films. The purpose of this research is to understand how the electrical- and magneto-transport properties in La0.67Ca0.33MnO3(LCMO),La0.8Ba0.2MnO3(LBMO),La0.67Sr0.33MnO3(LSMO(113)) and La0.67Sr1.33MnO4 (LSMO(214)) thin films, at various magnetic fields and temperatures. First of all, we demonstrate that the LSMO(214) and LSMO(113) can be sensitively affected by magnetic states on the manganite films. Our result provides further understanding of the dielectrics variation during the phase transition from an AFM insulating phase and/or a ferromagnetic metallic phase to a paramagnetic PM metallic phase. It is known that the strong correlation between the itinerant carriers and the local magnetic moments is the mechanism for FM/PM phase transition for LSMO(113), while the direct magnetic exchange coupling governed the AFM/PM phase transition and an indirect coupling to the status of intrinsic carriers for LSMO(214) films. These transitions can not be concludes directly by using a dc resistance measurement but can be clearly distinguished by the CIS measurement. On the other hand, the dc resistance (Rdc) and the relaxation time(£n) have the same tendency that this indicates the changes of £n matches to the electric transport properties for LCMO_90min and LSMO(214) thin films. We focus on the the dielectric properties of both samples are insensitive to temperature, revealing that the dielectric behavior is independent of magnetic phase transition but strongly associated with the transport properties. Therefore, the magnetic transitions can be most thoroughly investigated by combining CIS measurements and RC ECM, as well as by making dc resistance measurements. Moreover, the relative change of M£q(ac) is nearly larger than the dc resistive variation. This phenomenon, called giant magneto-impedance effect (GMI), implies that thehigh-frequency magnetotransport effect may enhance the performance of these manganese oxides for sensing the magnetic field. The CMI, have been analyzed by ECM, including two sets of parallel R and capacitance (C) components in series. The analyzing results the specific feature of grain boundaries(GBs) can be attributed to the interplay of magnetic moment spin disorder to ordering. The grain boundary (GB) effect can enhance low field magnetoresitance (LFMR) for artificial GBs, but shows very limited enhancement for those GBs in epitaxial films. This study finds that artificial GBs, which exhibit large LFMR, can be modeled as a non-conductive layer which disconnects the lattice periodicity of adjacent grains and contains no magnetic ions. The GBs in the present fully strained epitaxial film, which shows a relatively smaller LFMR, are more similar to a semi-continuous grain with continuous distribution of magnetic ions that align loosely parallel to the grain magnetic moment. In addition, we report in this study the high frequency magneto-transport properties, based on the classical model, of La0.8Ba0.2MnO3 and La0.67Ca0.33MnO3 thin films around their ferromagnetic transitions and under an external magnetic field. It is found that the specific features of magneto-impedance can be correlated with the complex magnetization response and the dielectric relaxation in corresponding phase states. The fast dielectric relaxation time, £nE, and the slow magnetic response, £nH, reflect the interplay of itinerant carriers and the magnetic coupling to the ac electromagnetic wave, indicating that the double exchange, or hopping, of carriers between O 2P and Mn 3d-eg states occur prior to the indirect magnetic coupling of adjacent Mn ions via strong Hunt¡¦s rules. Applied magnetic field enhances both electric and magnetic dipoles are now responding faster to the electromagnetic wave. The results of our work may provide a fundamental understanding of high frequency magnetic and electrical properties of the manganite films, and imply tips for device application of the films.

Laser-atom interactions create atomic coherence and large nonlinear atomic polarization. We investigate resonant laser-atom interactions to generate large nonlinearities and control them using magneto-optical fields. Coherent control of high-order susceptibilities and magneto-optical rotation are demonstrated. Experiments are supported by theoretical studies that effectively describe the observed phenomena. It is shown that a new coherent field, with polarization orthogonal to a weak signal field, can be parametrically generated via an all-resonant four-wave-mixing process. This is demonstrated in a double-ladder system having two intermediate states between a ground and an excited state. It is shown that the parametricgeneration process can be coherently controlled by coupling lasers and magnetic fields. It is theoretically established that the underlying physics is a resonant three-photon process with a wide domain of control parameters. Electromagnetically induced transparency (EIT), where absorption of a weak probe is suppressed via quantum interference, is demonstrated in a usual three-level ladder system. It is observed that in contrast with EIT in a usual ladder system, addition of a second channel helps to suppress the absorption of two weak probe fields in the double-ladder system. The resulting enhancement of transmission in two different channels is due to gain caused by three-photon processes. Coherent control is strongly limited by coherence lifetime, which is the inverse of the dephasing rate. A lambda-system, having two ground states coupled to a common excited state by lasers, can generate a new eigen (dark)-state that is transparent to incoming fields and hence suppresses fluorescence. However, ground-state dephasing perturbs the dark state. A new method for measuring the ground-state dephasing rate from fluorescence signals is proposed and a proof-of-principle experiment demonstrated. While two laser fields in a lambda-system are resonant with their respective transitions, the atomic polarizations are very sensitive to an applied magnetic field. This effect can be used for optical magnetometry. The degree of sensitivity of the magnetometer is determined by two competing parameters–atomic density and laser intensity. It is shown experimentally that the optimal sensitivity reaches saturation, which is contrary to the idea that sensitivity increases indefinitely with an increase in the above parameters.

In this thesis, the study of optical properties of magnetic fluid thin films is the main purpose. We measured the intensity of linear polarized laser beam, which passed through our sample, magnetic fluid thin film with external magnetism, to analyze the relationships between magnetic field intensity and magneto-birefringence and magneto-dichroism. According to our experimental results, we ascertain that both the magneto-birefringence and magneto-dichroism are existed. Besides, we found that the difference of index at magnetic fluid thin film changed with magnetic field intensity also. The phenomenon let us believe that magnetic fluid thin film is anisotropy. Moreover, we also applied the statement, which agreed by most physicists to explain what we found from our real measurements.

Nano-sized particles are widely regarded as a tool to study biological events at cellular and molecular levels. However, there are only a few imaging modalities that can visualize interactions between nanoparticles and living cells. A new technique -- pulsed magneto-motive ultrasound imaging, capable of in-vivo imaging of magnetic nanoparticles at improved depth and in real-time is introduced in this study. In pulsed magneto-motive ultrasound imaging, an external high-strength pulsed magnetic field is applied to induce motion within magnetically labeled tissue and ultrasound is used to detect the induced internal tissue motion. A laboratory prototype of a pulsed magneto- motive ultrasound imaging system was built, tested and optimized through modeling and experimental studies using tissue-mimicking phantoms, ex-vivo tissue samples and in- vivo mouse tumor model. The results demonstrated a sufficient contrast between normal and iron-laden tissue labeled with ultra-small magnetic nanoparticles. Finally, further modifications and research directions are discussed which can eventually lead to development of a clinically applicable pulsed magneto-motive ultrasound imaging system. / text

This project focused on two aspects of magnetite thin films. The first was to find optimum parameters and conditions for deposition of stoichiometeric Magnetite films using pulsed laser deposition (PLD). The second aspect was the characterization of the magnetic and electrical properties in order to broaden the spectrum of understanding of PLD Magnetite films. These properties were also investigated in terms of the substrates on which the films were deposited. Discussed in this thesis are deposition parameters, structural characteristics, magnetic and electrical characteristics of the films in terms of different substrates and film thicknesses. The discussion consists of structural parameters obtained using X- ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), and electric properties such as resistance as a function of temperature and voltage dependence on the applied current. The magnetic properties measured were the magneto-resistance, M-H hysteresis loop, and magnetization as a function of temperature. The results obtained are then compared with pre-existing literature data. It will be shown that there is an impurity phase that may be seen when magnetite films are deposited on Sillicon dioxide substrates.

A novel material characterization method for magneto-dielectric composite material was proposed. MD materials have been reported as providing new opportunities for effective antenna size reduction in many studies. Since MD materials have to be realized through material synthesis, an accurate measurement method is required to extract them. The proposed method, cavity perturbation technique using substrate integrated waveguide cavity resonator, has been demonstrated through theories, simulations and measurement that it can be used to extract both electric and magnetic properties of the MD composite material effectively. MD materials using cobalt-fluoropolymer have been synthesized and material design guidelines for antenna applications are also provided. The benefits of using MD materials on antenna miniaturization was also demonstrated by comparing the performance of an antenna on MD material to other antennae on high dielectric constant materials and FR-4 material. Through simulations and measurements, the MD material is a promising solution for next generation smartphone or wearable type applications.

For several decades, the field of magneto-optics (MO) has demonstrated applications that have impact on every day applications such as in optical data storage, magnetic field sensing, crucial for magnetoencephalography and magnetocardiography; and compact and efficient optical isolators, among others. In the past, many of these applications and the devices designed for them have heavily relied on inorganic materials. Organic materials with a high MO response represent an interesting alternative to the inorganic equivalent by not only being a more cost efficient solution, but also by allowing the user to modify a number of variables to control and optimize the MO performance depending on the application and level of performance desired. In this dissertation I discuss the MO properties of novel organic materials, starting with polythiophene, which has been of interest due to the strong relationship between its high MO performance and its lamellar structure and regioregularity. I will also be discussing another material system that provides several degrees of MO tunability: magnetite based nanocomposites. A unique and novel synthetic approach described in this dissertation yields both highly transparent and MO responsive polymer films. I will be describing a systematic approach that indicates a strong influence of the size of the nanoparticle as well as the nanoparticle concentration in the MO performance of the bulk polymer, while maintaining high optical quality with minimal scattering and absorption in the visible and near infrared. Finally, I will be discussing the implementation of both a magnetite nanocomposite and a cobalt ferrite based nanocomposite in a free space magnetic field system and demonstrate the proof-of-principle operation of a sensing system.

No description available.

This work is comprised of the study of two magneto-optical phenomena: the Kerr effect and the Faraday effect. Neutron physics experiments often utilize polarized neutrons, and one method to generate or guide polarized neutrons involves the use of a system of magnetic super-mirrors. Experience shows that the magnetization of the super-mirror may decay with time; therefore, we implemented the surface magneto-optical Kerr effect (SMOKE) to study the temporal behavior of the magnetization of a magnetized remnant super-mirror sample, where a sensitivity of 0.1 mrad was obtained. Unique to our set-up was the method in which the various magnetization directions were probed. The sample was magnetized prior to insertion into the set-up, and a high precision rotational stage was used to manually rotate the sample to effectively generate a reversal of the magnetic field. Multiple samples from a larger super-mirror specimen were tested, in which no change in the magnetization was detected for one month after sample magnetization. Further studies could increase the sensitivity of the experiment, potentially rendering the method as an application for real-time magnetization monitoring. Polarized 3He nuclei are often used as an effective polarized neutron target at various laboratories, including Jefferson Lab, through the use of spin-exchange optical pumping in a glass cell constructed of GE-180. Utilizing the nuclear spin optical rotation to measure the Faraday effect of polarized 3He would develop a new procedure for polarization monitoring, establish a powerful tool to diagnose the wall properties and thicknesses of the cells used, and the determination of the frequency independent magnetic component of the polarizability would ultimately lead to the extraction of the spin polarizability of 3He. Furthermore, this study has the future implications of being the pioneer experiment for terrestrial dark matter studies. A new triple modulation technique was devised, where a sensitivity of 60 nrad was obtained, and the first ever extraction of the Verdet constant of GE-180 was recorded, an important factor in wall thicknesses and diagnostic investigations for Jefferson Lab. However, a measurement of the nuclear spin optical rotation of a polarized 3He target was not realized, as the measured polarization suggests a Faraday rotation just below the 60 nrad threshold. Nevertheless, the devised triple modulation method proves to be a very sensitive probe in Faraday effect studies, and additional examination of the polarized target for the production of a larger polarization, should yield a measurement of the nuclear spin optical rotation of polarized 3He.