Magnetisation precessional dynamics have a great role in ferromagnetic thinfilms and nanostructures, where the underlying mechanisms of intrinsic and extrinsic damping are crucial for spintronic and magnonic devices. This important role drives the research activity with a goal of acquiring a better understanding and the ability to tune magnetic damping properties as desired. Research has tackled these issues through many routes linked with the ferromagnetic material type or thickness, while others have tried different aspects by including other nonmagnetic or ferromagnetic elements as dopants or adjacent layers. The effect of the additional nonmagnetic materials on the magnetic damping in ferromagnetic system is the focus in this thesis, where a range of implementations of the nonmagnetic material was studied. The role of nonmagnetic layer on damping is shown in this study as the evolution of damping as the thickness of this capping layer developed gradually from none to a partial and to a full covering layer. The effect of nonmagnetic elements was also shown when the changes of the interface takes place, the magnetic damping depends on the development of the interface and the reduction of the NM capping layer is also demonstrated. These routes helps to establish an understanding of damping and the underlying mechanisms. Linking magnetic damping with other dynamic magnetisation phenomena gives an insight into the reversal behaviour mediated by domain walls in ferromagnetic systems. Studying jointly the contributions of damping and interfacial Dzyaloshinskii- Moriya Interaction gives a better insight into the factor effecting the magnetisation dynamics. As the understanding of the magnetic damping became clearer and the underlying mechanism and effects, linking between two-magnon scattering, spinpumping and spin-mixing conductance with the crystal structure give more information. This understanding and theory initiated a study to test the theory with a new route to control magnetic damping through modifying the contributions to the total magnetic damping that come from the individual atomic layers that make up a ferromagnetic thin-film. This showed outstanding results consistent with theory and demonstrating very low damping in a new synthetic ferromagnet.

Trapped atomic ions are a promising candidate system for developing a quantum computer. All elementary operations for quantum information processing have al- ready been achieved in trapped-ion systems with errors below the “fault-tolerant threshold”, meaning that these errors are sufficiently small to be removed with quan- tum error correction. However, the preservation of quantum information over the short timescales that are relevant for quantum computing has not, to our knowledge, been measured before in trapped-ion qubits. Previous investigations have measured decoherence over long times and extrapolated an exponential decay model to short times. We directly measure the qubit memory error rate over short timescales, which is made possible by the high-fidelity single-qubit gates and state preparation and mea- surement in our system. Our qubit is a hyperfine “atomic clock” transition in 43Ca+, and gates are applied with near-field microwaves. We find that the assumption of exponential decay of qubit state coherence does not apply in our system. The data is fit well by a model of 1/f frequency noise with a low-frequency cutoff. The small- est memory error that we measure is 3(1)×10−6 over 2ms. The time at which our qubit memory error is 1×10−3, an important threshold for viable quantum error correction, is ≈400ms. We also present a design study into a new ion trap electrode geometry for applying near-field microwave two-qubit gates. This design features an ‘S’-shaped meander electrode to passively null the microwave field at the ions’ locations. It has improved isolation between the meander and other electrodes compared to previous work on this, which should reduce the sensitivity of the microwave field distribution to the boundary conditions of these electrodes. We show that the trap would allow for ion chains to be trapped, transported and split with feasible DC and RF voltages.

This thesis explores the influence that morphology plays in hybrid organic/inorganic solar cells. This is studied for a range of different materials systems. A series of cadmium xanthate complexes were synthesised, for use as in-situ precursors to CdS nanoparticles in hybrid poly(3-hexylthiophene-2,5-diyl (P3HT)/CdS solar cells. The heterojunction morphology of these hybrid P3HT/CdS blends was found to be dependent on the ligand moiety of the precursor used. The formation of CdS domains was studied by time-resolved materials characterisation techniques and directly imaged using electron microscopy. A combination of transient absorption spectroscopy (TAS) and photovoltaic device performance measurements was used to show the intricate balance required between charge photogeneration and having percolated domains in order to effectively extract charges to maximize device power conversion efficiencies. An analogous method was also applied to a P3HT/Sb_2 S_3 system. Following on from the previous work, a non-toxic alternative to CdS and Sb2S3 was explored. Bismuth xanthates were thermally decomposed to form hybrid polymer/Bi_2 S_3 heterojunctions with two distinctly different morphologies. The bismuth xanthates were found to form nanorods in-situ, within the solid-state polymer matrix, as well as mesostructured arrays of Bi_2 S_3 rods that were later infiltrated with a polymer, using a two-step method. TAS was used to study the charge generation yield in both these systems and hybrid photovoltaic devices were also fabricated. Finally, through a collaboration with The Institute of Photonic Sciences (ICFO), TAS was used to study two separate organic semiconductor/Bi_2 S_3 BHJs. The first of which was a P3HT/Bi_2 S_3 nanoparticle blend solar cell. The charge generation yield in this system was investigated and then compared to a novel thiol-functionalised P3HT based block copolymer (P3HT-SH). Secondly, TAS was used to obtain a better understanding of the charge transfer at several interfaces in a vertically structured Bi_2 S_3 nanorod array that was filled with 2,2',7,7'-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (SPIRO).

A flexible wide-field fluorescence lifetime imaging (FLIM) endoscope is developed for clinical applications. For remote imaging, a coherent fibre optic bundle was used which required techniques and protocols to be developed to minimise artefacts associated with dispersion and recover accurate lifetime estimates. Potentially gain switched pulsed laser diodes are better suited for the clinic than light sources used conventionally for FLIM endoscopy because they are more compact and lower in cost. By imaging ex vivo human tissue samples, it was demonstrated that gain-switched pulsed laser diodes are a viable alternative excitation light source. The system was able to acquire ∼mm-scale spatial FLIM images from fresh ex vivo diseased human larynx biopsies. For wide-field FLIM with the fastest update rates, gated optical intensifiers (GOIs) are used as detectors. This thesis documents the characterisation of next generation GOI technology that can achieve larger than existing standard GOI standard gate-widths for improved light efficiency and that use a magnetic field to enhance spatial resolution beyond that of proximity focusing alone. For intra vital microscopy, access to tissue surfaces deep inside hollow or solid organs is challenging for microscopes. This thesis applies a commercially available confocal laser scanning endomicroscope (CLSE) adapted for time correlated single photon counting (TCSPC) FLIM to study protein interactions using based on Förster Resonance Energy Transfer (FRET) between fluorescent proteins. Protocols to minimise artefacts associated with dispersion in the CLSE’s fibre probe to recover accurate lifetime estimates are presented. To validate the design, the CLSE was used for a time-lapse study of live cancer cells in vitro to monitor their response to an inhibitor of the ERK intracellular signalling pathway by FLIM FRET of an extracellular signal-regulated kinase (ERK) biosensor.

The large amount of new high energy data being collected by the LHC experiments has the potential to provide new information about the nature of the fundamental forces through precision comparisons with the Standard Model. These precision measurements require intensive perturbative scattering amplitude computations with large multiplicity final states. In this thesis we develop new on-shell methods for the analytic computation of scattering amplitudes in QCD which offer improved evaluation speed and numerical stability over currently available techniques and also allow us to explore the structure of amplitudes in gauge theories. We apply these techniques to extract compact analytic expression for the triple collinear splitting functions at one-loop in QCD and supersymmetric gauge theories which contribute to the universal factorisation at N${}^3$LO. We also investigate improvements to dimensionally regulated one-loop amplitude computations by combining the six-dimensional spinor helicity formalism and a momentum twistor parameterisation with the integrand reduction and generalised unitarity methods. This allowed the development of a completely algebraic approach to the computation of dimensionally regulated amplitudes in QCD including massive fermions. We present applications to Higgs plus five-gluon scattering in the large top mass limit and top pair production with up to three partons. In the case of massive one-loop amplitudes we present a new approach to the problem of wave-function renormalisation which only requires gauge invariant, on-shell building blocks. Massive one-loop amplitudes contain information that cannot be extracted from unregulated cuts, the new approach instead constrains the amplitudes using the universal poles in $6-2\eps$ dimensions which can be computed from an effective Lagrangian on dimension six operators.

In this thesis, the Initial Mass Function (IMF) is studied using the Stochastically Lighting Up Galaxies software suite (SLUG), a package of tools including a stochastic Stellar Population Synthesis (SPS) code and associated analysis packages, including a novel Bayesian inference framework. Following an introduction to some core concepts, new developments of the SLUG code are described. These include a variable IMF capability which is then applied to broad-band photometry taken from the Legacy ExtraGalactic Ultraviolet Survey (LEGUS), a Hubble Space Telescope treasury programme. The physical parameters of star clusters in galaxy NGC 628 are inferred using SLUG's Bayesian inference tools. We find that the posterior probability distributions of the high-mass slope of the IMF are very broad, and we quantify a degeneracy between the IMF and the cluster mass. The inclusion of additional photometric data (Ha) is found to provide some improvement. However, using mock cluster models we found that only through constraining the mass of the cluster through photometrically-independent means is it possible to accurately recover the IMF slope. An additional source of information is the UV spectrum, which is dominated by the massive stars whose populations are affected by the high-mass region of the IMF. To be able to exploit this region of the spectrum effectively using equivalent width measurements, the resolution of SLUG's UV spectral synthesiser requires improvement. To this end, the implementation of a high-resolution UV synthesiser is described, and then put to use in a theoretical study of the IMF using mock observations generated with SLUG. The constraining power of UV spectral features when combined with broad-band photometry is quantified, resulting in significant improvement in IMF slope recovery. Finally the results and limitations of the studies are discussed, and recommendations are made for future studies and improvements.

The scientific questions addressed in this thesis divide into fundamental cosmology and galaxy evolution, although divergent in theme these are connected by the use of high multiplex spectroscopy. Specifically, we employ spectroscopic galaxy redshift surveys to probe the connection between galaxies and the Cosmic Microwave background, and to link galaxies to neutral gas reservoirs which contain fuel for star-formation. We present the following observational investigations: 1. A spectroscopic redshift survey of $\sim$7000 galaxies in the core of the Cosmic Microwave Cold Spot, with the aim of following up the claim of a supervoid capable of imprinting the Cold Spot via the Integrated Sachs-Wolfe effect. Using 2dF+AAOmega we have surveyed 66 deg$^2$ out to $z < 0.5$, using a $i\leq19.2$ magnitude limited selection based on imaging from the VST-ATLAS Survey. We confirm the presence of a void at $z=0.14$ with a scale radius of 119h$^{-1}$ Mpc and a density contrast of $\delta_{m}=-0.34$, however it is deeper and much less extended than previously claimed. The $\Lambda$CDM ISW imprint of this void is only -6.25 $\mu$K, compared to the Cold Spot’s central temperature of $\sim$150 $\mu$K . We detect further under-densities at $z=0.26$ and $0.30$, although these contribute even less to the temperature decrement than the larger $z=0.14$ void. When combined with previous data we can exclude a large contribution to the Cold Spot from a void at $z < 1$, at higher redshift the ISW effect is less significant. Similarity between our control field and the Cold Spot survey places constraints on any non-standard attempt to link the voids to the CMB Cold Spot. 2. An integral field survey of six $z\simeq3.5$ Damped Lyman $\alpha$ systems with MUSE, to search for host galaxies and to study their environments. Our survey did not preselect DLAs based on absorption properties, on the contrary of current leading DLA host searches that select only high metallicity systems. MUSE has revealed that three of the six fields contain bright Lyman $\alpha$ emitters (LAEs) with a few hundred km s$^{-1}$ of the absorption redshift, detecting associated galaxies out to larger impact parameters than was previously possible. In one field (J0255+0048) we discovered an extended Ly$\alpha$ nebula in close proximity to the DLA, extending up to 50 physical kpc from the DLA location. The object has a striking correspondence between absorption and emission components, which may indicate the structure is an ongoing merger with tidal debris at the DLA location. Our most metal-poor system (J1220+0921) was revealed with MUSE to be embedded in a dense filament-like structure, which extends across the full MUSE field of view (380 kpc). We have compared the distribution of galaxies around the DLAs to models and simulations, using the {\sc eagle} hydrodynamical simulation and a model based on the {\sc galics} semi-analytic prescription. Using these mock data we have shown our observations are consistent with both {\sc eagle} and simple halo prescription put forward to explain the strong clustering of DLAs. Furthermore we show how an expanded version of our survey may provide useful constraints on the small scale clustering of DLAs and the link between neutral gas reservoirs and star-formation.

Platinum (Pt) has widely been used for interface driven spintronics applications due to its strong spin-orbit interaction. Pt has been reported to experience spin polarisation when placed in close proximity to a ferromagnetic (FM) material thereby influencing many spintronic phenomena. Consequently, the effect of proximity induced magnetization (PIM) in Pt is studied in this thesis with a detailed investigation of the mechanism and the implications of PIM on magnetoresistance measurements. In this work, CoFeTaB (CFTB) is the FM material investigated. Structural and magnetic characterisation of CFTB/Pt, Pt/CFTB and Pt/CFTB/Pt samples were made in order to investigate PIM at the interface. X-ray reflectivity (XRR) and x-ray diffraction (XRD) were performed on these samples, where asymmetry in the Pt density and the crystalline texture were observed at the top and bottom interfaces. XRD measurements show the Pt crystalline texture depends on the CFTB thickness for the CFTB/Pt interface, but no significant thickness dependence was observed for the Pt/CFTB interface. The magnetic depth profile of the CFTB layer was obtained with polarised neutron reflectivity (PNR), which shows magnetisation grading. An asymmetry in Pt magnetisation was found between the two interfaces using x-ray resonant magnetic reflectivity (XRMR) with a higher moment at the top interface and lower at the buffer interface, giving a similar CFTB thickness dependence as the XRD results. This indicated that the Pt magnetisation depends slightly on Pt texture at the interface. No PIM was found in a YIG/Pt bilayer and the Pt XRD texture was poor, supporting a possible link of Pt polarisation to crystalline the morphology at the interface. Magnetoresistance investigations in three geometries performed on Pt/CFTB and CFTB/Pt bilayers were used to decouple the magnetoresistance contributions as a result of the anisotropy of the sample, spin Hall effect and other processes. The spin Hall MR ratio obtained was ~0.2 %, with an additional contribution with a cos θ dependence of ~0.1 %, which is a result of the impact of PIM generated spin current. No evidence of the Rashba effect was found in the symmetric CFTB/Pt/CFTB sample. Also, residual plots indicated the presence of higher harmonics that are dependent on the magnetisation direction. Temperature dependent proximity induced magnetism in Pt in contact with CFTB was presented, with PNR providing the magnetic sensitivity to the FM layer while the XRMR provide sensitivity to Pt magnetisation. PIM scales linearly with CFTB magnetisation which is inconsistent with the Pauli susceptibility. Significantly, a threshold CFTB magnetization is required for PIM to occur. Therefore the asymmetry in PIM at Pt/CFTB and CFTB/Pt interface is attributed to different magnetic susceptibilities at these interfaces.

From studies of fundamental physics to quantum technologies the production of ultracold molecules will have a huge impact across a range of applications. For many years laser cooling, which became an invaluable tool in cold atomic physics, was deemed to be too impractical for application to molecules. Nevertheless, laser cooling has now been demonstrated for a few molecular species. Using a frequency-chirped laser slowing technique, the velocity distribution of a pulse of CaF molecules is compressed and slowed from 180 m/s to about 10 m/s. These slow molecules are then captured in a magneto-optical trap. I present measurements that show how the number of molecules, the photon scattering rate, the oscillation frequency, damping constant, temperature, cloud size and lifetime depend on the key parameters of the magneto-optical trap, especially the intensity and detuning of the main cooling laser. The trap contains up to 2*10^4 molecules, the maximum photon scattering rate is 2.5*10^6 s-1 per molecule, the maximum oscillation frequency is 100 Hz, the maximum damping constant is 500 s^-1, and the minimum rms radius of the trapped cloud is 1.5 mm. A minimum temperature of 730 microkelvin is obtained by ramping down the laser intensity to lower values. To reach lower temperatures, the cloud is loaded into a blue-detuned optical molasses, which cools the molecules to 55 microkelvin, well below the Doppler-limiting temperature. I characterise the cooling process and suggest the sub-Doppler mechanisms responsible. These ultracold molecules are the optically pumped into a single quantum state, and coherently transferred between selected hyperfine components of the ground and first-excited rotational states. Finally, the ultracold, state-selected molecules are loaded into a magnetic trap that has a lifetime of about 1 s.

This thesis reports the first measurements of the ground state binding energies of CsYb molecules and the scattering lengths of the Cs+Yb system. The knowledge gained from these measurements will be essential for devising the most efficient route for the creation of rovibrational ground state CsYb molecules. CsYb molecules in the rovibrational ground state possess both electric and magnetic dipole moments which opens up a wealth of applications in many areas of physics and chemistry. In addition, we present the setup of a crossed beam optical dipole trap and the investigation of precooling and loading of Yb into the dipole trap. Evaporative cooling in the dipole trap results in the reliable production of Bose-Einstein condensates with $4 x 10^{5}$ $^{174}$Yb atoms. We also describe the necessary changes required to cool fermionic $^{173}$Yb atoms and report the production of a six-component degenerate Fermi gas of $8 x 10^{4}$ $^{173}$Yb atoms with a temperature of 0.3~$T_{\rm F}$. As well as the ability to cool Yb to degeneracy, we present the production of Bose-Einstein condensates containing $5 x 10^{4}$ $^{133}$Cs atoms. Effective cooling of Cs is achieved using Degenerate Raman sideband cooling, which enables $6 x 10^{7}$ Cs atoms to be cooled to below $2 \, \mu$K and polarised in the $\ket{F=3, m_{F}=+3}$ state with 90~\% efficiency. Finally, we report the production of ultracold heteronuclear Cs$^*$Yb and CsYb molecules using one-photon and two-photon photoassociation respectively. For the electronically excited Cs$^*$Yb molecules we use trap-loss spectroscopy to detect molecular states below the Cs($^{2}P_{1/2}$) + Yb($^{1}S_{0}$) asymptote. For $^{133}$Cs$^{174}$Yb, we observe 13 rovibrational states with binding energies up to $\sim$500\,GHz. In addition, we produce ultracold fermionic $^{133}$Cs$^{173}$Yb and bosonic $^{133}$Cs$^{172}$Yb and $^{133}$Cs$^{170}$Yb molecules. From mass scaling, we determine the number of vibrational levels supported by the 2(1/2) excited-state potential to be 154 or 155.