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In this thesis, a systematic Monte Carlo simulation study of confined nematic and cholesteric systems is carried out. A simple off-lattice model is developed to explore a range of confined systems. Double emulsion nematic shells are investigated with planar anchoring which is then extended to solid particles of different geometries with nematic coatings before progressing to single and n-fold toroidal droplets. For shells and coatings with planar anchoring the total topological charge on both surfaces must be +2. A bipolar structure is found in thick shells and four s=+1/2 defects are found for thin nematic shells. A metastable defect configuration comprising of two s=+1/2 and one s=+1 defects is occasionally observed for intermediate thicknesses. With the addition of chirality, a transition to a twisted bipolar director configuration is observed at all thicknesses. A single toroidal droplet with planar anchoring has a defect free ground state. Previous work has predicted the presence of a twisted director configuration ground state. The relative stabilities of the twisted and untwisted configurations are investigated here. It was found that, for all the systems investigated, the twisted director configuration is only stable for a cholesteric torus. For multiple tori system, with each additional handle the total topological charge on the surface decreases by 2. In a non-chiral nematic system the constraint on the topological charge on the surface is fulfilled by the required number of s=-1 defects located at either the innermost surface of a handle or the join between two tori. With increasing chirality, the s=-1 defects detach from the surface and migrate to form s=-1/2 disclination lines through the cholesteric. In handled droplets with homeotropic anchoring, two s=+1/2 disclination lines are found that, with the addition of chirality form a helical structure around the tube.

Understanding the transport properties of microorganisms in fluid is a fundamental problem in soft matter physics, and the dynamics of an active colloid in non-equilibrium statistical mechanics has recently attracted pioneering investigations into the design of artificial swimming robots at the microscale. A topical review of the remarkable discoveries in the field, both theoretically and experimentally, is first addressed. The mechanism of interfacial phoretic transport is used for an active colloid achieving autonomous propulsion by diffusiophoresis. A theoretical framework has been established to ascertain the generic properties of the active motion of such a self-propelled colloid, driven by the use of surface catalytic reactions. The kinetic route for the chemical reaction is considered as a two-step process, followed by quantitative procedures that examine the influence of fuel concentration and colloid size on the propulsion velocity. Specifically, both Janus and inhomogeneous colloids are studied, and their propulsion velocities rise linearly with the fuel concentration in a dilute solution and decay with the size scale in the small size limits. The theoretical results for a Janus sphere are consistent with the experimental observation. Furthermore, to what extent can the incorporation of advection into the diffusion be interpreted as a means of self-propulsion. An advection-diffusion model is constructed to compute the concentration distribution of the solute and propulsion velocity, aiming to explore the role played by the advection effects on the movement of Janus particles. The numerical results show that while Janus particle can achieve an autonomous propulsion at a small P\'eclet number, the accumulation of solute particles in the upstream of the colloid disappears at the large Pe limit. In conclusion, the major outcome of this work is the demonstration of the qualitative agreement with the present analysis of mobility to explain the observed size dependence. Lastly, the results suggest that a catalytic colloid powered by diffusiophoresis is a useful model for self-propulsion and indicate what still needs to be done to obtain a full understanding of the swimming characteristics of colloidal dispersions.

The effects of magnetic fields on long-pulse (nanosecond) laser-plasma interactions have been a subject of research interest in recent years. Applied fields have been used for the formation and control of plasma waveguides (Froula 2009), for improving energy coupling under conditions relevant to indirect-drive ICF (Montgomery 2015) and have been observed to arise naturally in the gas-fill of hohlraums due to field generation by the Biermann battery mechanism at the wall (Li 2009). These systems are complicated by the range of coupled magnetised electron transport phenomena which can occur. For example, heat-flow across field lines is suppressed in a magnetised plasma and magnetic fields can rapidly advect along temperature gradients due to Nernst advection, an effect which is predominant at moderate magnetisations (wt ~ 1). This thesis addresses the question of how these phenomena, coupled with inverse bremsstrahlung heating, affect the hydrodynamic evolution of the plasma and in turn change laser self-focusing. This problem is investigated by means of theoretical and computational modelling. A paraxial wave solver has been developed and used in conjunction with the existing 2D plasma codes, CTC, an MHD code including a detailed model of Braginskii electron transport, and IMPACT, a Vlasov-Fokker-Planck code with fully implicit magnetic fields. Simulations of moderate intensity (~ 10^14 W/cm^2), 10 micron width infrared laser pulses propagating through under-dense (ne = 10^18 - 10^19 cm^-3) plasmas in the presence of 0 - 12 T applied fields demonstrate an inhibition to beam self-focusing and thermal pressure driven density channel formation resulting from Nernst advection over time-scales greater than ~ 200 ps. VFP simulations accounting for non-locality indicate that heat-flow and Nernst advection can be over-estimated however and result in a re-emergence of channeling phenomena under these conditions. Finally, the magnetothermal instability - the result of feedback between the Nernst effect and Righi-Leduc heat-flow - frequently arises, affecting temperature and field profiles and is considered in the context of such conditions.

The spin Hall magnetoresistance (SHMR) is a recently discovered effect that occurs in a normal metal (NM) that is in contact with a magnetic material. An insulating magnetic material is ideal as it prevents other magnetic effects by confining the electrons to the NM. To study this a new method for making yttrium iron garnet (YIG) has been developed using sputtering techniques so that devices are quicker and cheaper to produce than by existing liquid phase epitaxy (LPE). The YIG material magnetic properties were extensively characterised up to 280 nm thick. The magnetisation drops below the bulk value in thin samples believed to be caused by a contaminated layer at the substrate interface. As the SHMR is an interface effect the roughness of the films is important and was investigated by X ray reflectivity (XRR) and atomic force microscopy (AFM). The crystal structure was investigated using transmission electron microscopy (TEM). The SHMR is also significantly improved by a factor of 3 after treating YIG with piranha acid before metals are deposited on top. For SHMR measurements platinum was used first and provided similar results to what is found in the literature. The angular dependence has been measured in a cryostat using four probe resistance measurements with a split pair magnet that allows the sample to be rotated in any direction relative to the applied field. This shows excellent agreement with the theory and was studied for the temperature range of 1.5 K - 300 K. This data has then been fitted using various models for the spin diffusion length and the conclusion reached is that a variation of the Elliot-Yafet mechanism (EY) is the most likely explanation for the observed temperature dependence. The same effect was found to occur in tungsten but with the important difference that it has a negative temperature coefficient of resistivity. This has been successfully fitted with the same spin relaxation models as the platinum. The tungsten is not believed to be in the beta phase, something which if achieved in further work could allow the size of the effect be improved by an order of magnitude up to several percent and so potentially allow the effect to have applications in a device.

Artificial Spin Ice (ASI) have been fabricated from NiFe in the square geometry over areas 1-2mm^2. They have small enough volumes to be thermally active within an experimental temperature range. The dynamic hysteresis has been measured using a SQUID-VSM magnetometer. We found that larger dipolar interaction can stabilise the superparamagnetic behaviour and lead to increased order at low temperature. Variation in the observed average blocking temperatures, recorded via hysteresis and zero- field-cooled (ZFC) experiments, is attributed to the distribution of island sizes and interaction effects. A new synchrotron capability at the I10 beamline in Diamond Light Source (UK) has been implemented and used to measure islands as small as 30 × 70 × 8 nm^3. At this size, measuring the exact microstates of the individual nanomagnets is challenging. Although this method is a scattering process, it maintains sensitivity to the microstates of the system by using coherent X-rays to produce a speckle pattern. Dynamics were observed in the speckle pattern in the temperature range 180 - 250 K. The characteristic relaxation time was fitted to a Vogel- Fulcher law, with an activation temperature of 40±10 K and freezing temperature of 178±5 K. From magnetometry measurements and simulations we attribute the activation temperature as originating from the non-uniform magnetic structure at the ends of the islands. The freezing temperature relates well to the energy scale of the interaction. Finally, a full-field magnetic microscopy method to probe dynamic ASI has been demonstrated; transmission X-ray microscopy (TXM). The method uses circularly-polarised soft X-rays to probe the magnetic orientation of the individual nanoislands. We have developed an on-membrane heater and thermometer, which is capable of temperatures in excess of ≈ 700 K. We have used it to heat the ASI whilst tracking the individual vertex states. We have been able to measure the creation and propagation of emergent monopole excitations and observed increased avalanche velocities and magnetic mobilities at higher temperatures. The largest change in the magnetic mobility was found for the most strongly interacting array, increasing by 1.7±0.7mm2A−1s−1 for ∆T ≈ 30 K.

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Metal phthalocyanines prepared as single crystals and thin films have been analysed using a combination of microscopy and diffraction based characterisation. Vanadyl phthalocyanine (VOPc) and chloroaluminium phthalocyanine (ClAlPc) prepared as thin films on oxidised silicon at a variety of substrate temperatures are analysed by atomic force microscopy (AFM) and x-ray diffraction (XRD). Elevated substrate temperatures are found to promote larger morphological features and out-of-plane diffraction. In addition single crystals of VOPc are grown and the single crystal structure is re-determined. Thin films of copper iodide (CuI) are prepared, at a variety of substrate temperatures, and analysed using AFM and XRD. These films are found to be (111) oriented and are used as structural templating layers for sequential growth of VOPc and ClAlPc thin films. These structural templates are found to alter the structure of thin films of VOPc and ClAlP. VOPc is shown to adopt three distinct molecular orientations whereas ClAlPc is found to adopt only one. In addition to this the growth behaviours of VOPc and ClAlPc on thin films of CuI is explored using AFM and different growth modes are suggested. Single crystals of CuI are synthesised from solution for use as a model structural templating system and characterised using low energy electron diffraction (LEED), AFM and XRD. These crystals were oriented to their (111) face and subsequently used as a model template for the growth of VOPc. The films of VOPc are analysed using XRD and AFM and the (111) surface is found to promote one orientation of VOPc, suggesting that the molecules interact differently with a single crystal surface than with a polycrystalline thin film. Zn- and O-terminated (0001) Zinc Oxide (ZnO) crystals are prepared and used to investigate the effects of surface chemical termination on the growth of VOPc thin films. The ZnO surfaces are analysed using LEED, XRD and AFM and are found to adopt different surface reconstructions under identical preparation conditions. These surface reconstructions result in VOPc films which have different structures and morphologies.