Available Student Projects
We mainly have experimental activities i.e. offer a variety of measurements addressing materials properties (see our research pages for an overview). There are also a number of possible tasks involving numerical simulations (e.g. light scattering or micromagnetic), or improving control programs for experimental setups.
The effect of geometric imperfections on magnetic properties
How does internal and external geometric imperfections, i.e. voids and surface roughness, influence the magnetic and electric properties of bulk materials on a macroscopic scale? Computational models, i.e. finite element models, of bulk materials are commonly set up with perfect geometry/mesh and homogeneous material properties. The material properties used, such as the hysteresis loop, are extracted from carefully controlled “perfect” specimens and do not perfectly map to the bulk materials. The aim of this project is to quantify this mapping in relation to for example void distributions and surface roughness and to generalise the effects of imperfections on resulting magnetic properties.
Simulation and fitting of polarised neutron reflectivity data
The task within this project will be to simulate and fit polarised neutron reflectivity data from EuS/TM multilayers. Recently, strong room temperature magnetisation was observed in EuS/Co multilayers. In a series of neutron scattering experiments we have collected data that can be used to estimate experimentally the extension of the magnetic polarisation in EuS. You will use a specifically developed fitting tool for reflectivity data, called GenX. Resulting data will be combined with input from x-ray circular magnetic dichroism experiments in order to provide more reliable information. This project requires some basic knowledge about computer use and optionally programming.
Magnetotransport in amorphous nanoscale films and multilayers
Developing materials and devices where the magnetic and electrical properties are linked is the subject of the relatively new field of spintronics. This project involves studying the electrical transport properties of amorphous magnetic films. Amorphous magnetic films are attractive for spintronic devices due to their high degree of uniformity and potential for tuning of magnetic and electronic properties. Yet, the mechanisms defining their electrical properties are not well understood. The project will involve measurements of resistivity, Hall effect and magnetoresistance in nanoscale films from 10 K up to room temperature. Multilayers of alternating magnetic and non-magnetic layers will also be studied.
Magneto-optic spectroscopy of advanced materials
This project is focused on the exploration of energy dependent rotation of light from surfaces. The aim is twofold: Establish spectroscopic magneto optical of few elements and secondly to explore how thick a layer has to be to give the signature corresponding to the bulk like response.
Some transition metals are known to easily take up large quantities of hydrogen on interstitial lattice sites. For bulk materials, the thermodynamics and kinetics of such systems are quite well understood. In the case of thin films, this situation changes since the hydrogen-hydrogen interaction is mediated by elasticity, which is a long range force. As a result, thin film metal hydrides show profound finite-size and proximity effects. The changes of thermodynamics and/or kinetics can be well explored by different scattering methods.
The possibility to alter optical properties of materials by electrical, thermic or optical stimuli offers exciting new applications. Examples range from a usage in motorcycle helmets with visors of variable transmittance providing bikers the comfort of a dark visor in sunlight and the safety of a clear visor in the dark to applications which can have a global impact on energy consumption via passive regulation of heat flux in and out of buildings reducing heating & cooling costs.
The necessary changes in optical transmission can, for many materials, be related to the concentration of hydrogen in transition metal hydrides. However, for these materials a change in hydrogen concentration is needed in order to tune the transmission of photons. For O-containing YHx a different switching mechanism is reported. The darkening of the Yttrium-oxy-hydride YOyHx is stimulated by the illumination with sunlight. This photochromic behaviour has the distinct advantage that the material can automatically regulate a close to constant transmitted intensity. In this project, we will address this class of materials systematically. Our focus will be on revealing the mechanism of the photochromic reaction and control as well as improve the properties of the films.
Self assembly is one of the most fascinating phenomena in nature, since it can form well ordered structures on almost all length scales. The self assembly process is determined by the interaction between the constituents. Accordingly, a system offering tuneable interaction is an ideal playground for the understanding of the basic concepts of self assembly. We realize such a system by dispersing magnetic and non-magnetic particles in a ferro fluid matrix. Analysing the microscope images from such samples statistically gives quantitative information about phase formation.
Surface ordering under shear
In fluid mechanics, flow is described by the Navier–Stokes equation in the bulk and a no-slip boundary condition at the solid interface. However, recently, both experiments and theory have shown that on a microscopic scale liquids may undergo significant slip at a solid wall. The magnitude of the slip length and its relation to the relevant surface parameters on that it depends, are, presently, under intense discussion in the literature and not well understood on the nm length scale. We contribute to this issue by investigation of surface ordering in samples that show correlations on mesoscopic length scales as well as Newtonian liquids mainly by scattering techniques. In particular, the use of neutron scattering methods allows to access liquids in contact to solid substrates.
Topological interactions in polymers under shear
Complex liquids have unique flow properties, displaying behaviours between classical solids and liquids due to their broad distribution of relaxation times. The viscoelastic properties can generally be connected to the microscopic picture of the structure and dynamics of the constituents. On the microscopic scale, this information can be addressed by scattering methods and changes in the structure under shear have been investigated intensively in the past. However, experiments addressing the dynamics of complex liquids under shear are very scarce and even the structure of very high molecular mass polymer melts is not well understood since the Weissenberg effect prevents rheological experiments in a simple Couette geometry. Recently, we have designed a closed shear device specifically to fill both these gaps and performed first successful test experiments. This allows to investigate the topological interactions in highly entangled polymers under shear load systematically and in detail. The experimental results, mainly obtained from neutron small angle scattering and spin echo experiments, will be compared to theoretical expansions of the reptation model, like convective constraint release, as well as computer simulations recently performed in the group.
Magneto-plasmonics – Understanding the correlation between plasmons and magneto-optics
Plasmons are collective electronic resonances that have a huge impact on the optical properties of metallic materials and nanostructures. With optical diffractometry and ellipsometry in combination with measurements of the magneto-optical effects one has access to all optical properties of a material. With the advent of plasmonics and metamaterials one has the possibility to tune those properties by using nanostructures to control the reflectivity of the material or even the properties of the emitted light itself. This project will involve magnetic nanostructures and optical and magneto-optical measurements for characterization of magneto-plasmons.
On this page we only show a few examples. If you are interested in a visit and further discussions about ongoing and planned projects, please contact one of these people:
- Björgvin Hjörvarsson (overall responsible for the division's research program)
- Gabriella Andersson (e.g. magnetic materials, domain imaging)
- Petra Jönsson (e.g. amorphous magnetic materials, additive manufacturing, nanomagnetism)
- Vassilios Kapaklis (e.g. magnetic materials, optics, x-ray scattering)
- Gunnar Pálsson (e.g. hydrogen in metals)
- Max Wolff (e.g. hydrogen in metals, solid-liquid interfaces, neutron scattering)