Materials Physics

The research in materials physics is based on synthesis and analysis of modern materials, both for understanding fundamental physical phenomena and for contributing to further development of new technology where material properties, right down to the atomic level, are crucial.

The core in the activity is in-house synthesis of materials and a continuous chain of subsequent experiments, from our own laboratories to large international facilities. Since we have control from the beginning to the end, we can find physical mechanisms behind the properties we observe, and thus gain tools for optimizing the materials further, e.g. through composition and placement of atoms.

Examples include a wide range of topics: phase transitions both in systems of magnetic nanostructures and in atomically thin metallic layers that absorb hydrogen, fine-tuned strength of amorphous and crystalline magnetic materials that can be developed to sensors or permanent magnets, and mechanisms behind the water purification functionality of African moringa tree seeds.

The term Soft matter is used for materials that have properties between those of hard solids and regular liquids. The materials are soft or easily deformed. They may be either elastic or viscous or have a combination of these properties.

The term Soft matter is used for materials that have properties between those of hard solids and regular liquids. The materials are soft or easily deformed. They may be either elastic or viscous or have a combination of these properties.

Many applications of soft matter are important in industry, biology and everyday life. The materials are often made of polymers, colloids or nanostructured systems. Examples include drug delivery systems, paints, coatings and many natural products as well as gels, rubbers and plastic materials.

Current research in this area includes studies of interactions of dispersed particles, the effects of external influences such as electric fields or stress on structure and phase behaviour. A particular interest has been to study relationships between structure and properties and in-situ investigation of samples under flow is a speciality.

A further area of activity is the study of adsorbed and self-assembled layers at interfaces. The design and preparation of interfacial structures is crucial to many modern materials and we apply a wide range of analytical tools to this problem.

Understanding interfaces and dispersed particles is important for many applications: water purification using novel flocculants has been a focus and attracted wide interest.

Further information about some of the terminology in this area can be found in the Glossary of Colloid and Polymer Science that has been made available as a teaching resource.

Hydrogen is the lightest element in the periodic table. It is a main component in most organic materials and forms hydrides with high hydrogen content when introduced into many metals. It also affects the electronic structure of the metal when absorbed.

The hydrogen nuclei (protons) are highly mobile in the metal hydride lattices and at lower temperatures there are strong effects of quantum tunnelling. This makes metallic hydrides interesting from a fundamental point of view, at the same time as their storage capacity is of potential use for energy systems with hydrogen as an energy carrier.

Hydrogen is the simplest atom for studies of e.g. quantum effects or of impurities in metallic lattices. Fundamental problems include screening of the proton charge by conduction electrons, vibrational states of the H-atom and transfer of H-atoms between different sites in a lattice by over-barrier or tunnelling processes. Complications arise when a proton is bound to another impurity, or when two or more protons are quantum correlated.

Among the application possibilities there is of course hydrogen as an energy carrier, e.g. in metal hydrides, where there has been a lot of activity during the last decades. Hydrogen is also highly relevant for vacuum technology, and the outgassing of materials is completely dominated by hydrogen at the lowest accessible pressures. Understanding of the hydrogen uptake of materials is therefore highly useful for obtaining desired material properties in these contexts.

Finally, the presence of hydrogen often modifies the properties (magnetic, electric, optical as well as mechanical and elastic) of materials. This allows tailoring of materials by hydrogen addition.

Magnetism is purely quantum mechanical in its nature. We investigate e.g. fundamental magnetic coupling phenomena, dimensionality aspects of magnetic materials, tailoring of magnetic properties, and some classes of functional magnetic materials.

 

Depending on the geometrical arrangements of atoms, of one or several species, different types of magnetic ordering will occur. The magnetic interactions, governing the relations between neighbouring magnetic moments throughout the material, depend on the electronic structure. For transition metals where the conduction electrons “cause” magnetism, properties can be tuned through alterations of the electronic structure, e.g. by altering structure or adding a suitable additional element. This addition of elements may both be permanent (alloying or implantation/doping) or reversible (hydrogen absorption and desorption).

Spin rotors

Interleaving of two or more distinctive metals in multilayers or superlattices gives additional possibilities for tailoring: a non-magnetic spacer could e.g. mediate parallel or antiparallel magnetic coupling between adjacent magnetic layers, or even isolate them from each other, all depending on the spacer thickness.

Making layers sufficiently thin, we actually reduce the spatial dimensionality of the magnetic material. This affects the fundamental thermodynamics of the magnetic phase transitions, according to universal theories. Effective dimensionality and ordering temperature can be controlled by the thickness of the magnetic layers. Other factors, e.g. crystal structure and spin dimensionality (presence or absence of magnetic anisotropy) determine the fine details.

The artificially structured materials (multilayers, superlattices, arrays of lithography-made islands, etcetera) are also a step towards improved functional magnetic materials. Here, we study mainly magnetic anisotropy, magnetotransport (field-dependent electrical resistance), optical properties and magnetization dynamics of both crystalline and amorphous samples, in close collaboration with other researchers doing predictive calculations.

Super ADAM, located at Institut Laue-Langevin (ILL) in Grenoble, France, is Sweden's first neutron reflectometer. The instrument is funded by VR, The Swedish Research Council (www.vr.se). Swedish users will be allocated at least 70 % of the beamtime each year.

With specular reflectivity we can determine the in-plane average structure of thin films in the range of a few nanometres to hundreds of nanometres. Neutron reflectivity is commonly used to study:

  • The depth distribution of light elements in soft matter such as polymer interfaces and solid/liquid interfaces.
  • The depth distribution of light elements, especially hydrogen, in thin films.
  • The depth resolved magnetic structure of thin films. Neutron reflectivity is sensitive to the absolute magnitude of the magnetic moment and its direction in-plane.
  • In addition, looking at the diffusely scattered radiation, away from the specular direction, we can learn things about micrometre sized in plane structures (for example magnetic domains).

Instrumentation Access

Applications for beamtime on Super ADAM should be submitted electronically using Electronic Proposal Submission system (EPS) via the ILL User Club. Proposals can be submitted twice a year, before the deadlines usually in February and September. If you are new to ILL please register as a new user via the User Club to have access to the EPS system.

Since Super ADAM is a part of the CRG (Collaborative Research Group) system, it is possible to obtain beamtime in two ways:

  1. Standard ILL beamtime (30% of total beamtime). Your proposal will be judged by an ILL Review Committee. In case of a successful application your experiment will be financially supported by the ILL (travelling, accommodation, meals).
  2. Super ADAM CRG beamtime (70% of total beamtime). Your proposal will be judged by the Super ADAM Review Committee. In this case proposals from Swedish institutions have priority.

Both types of proposals consist of the following parts: two-page description of the scientific case, which should be prepared in advance as a PDF file, and details about your sample (material, size, weight etc.) and sample environment (temperature, magnetic field, gas environment, solid/liquid cell etc.), which you add during the submission process. After the beamtime we can help you with the analysis of the data using different refinement programs, for example refinement with GenX.

You are welcome to contact the beamline scientists at Super ADAM as part of writing the proposal to get an idea of the feasibility, availability of equipment and resolution. The beamline scientists can also help you simulate the expected outcome of the experiment to assess the feasibility of the scientific case.

  • Alexei Vorobiev (magnetic colloids, magnetism)
  • Gunnar Karl Pálsson (hydrogen in metals, thin film magnetism, magnetic reference layers for soft matter)
  • Anton Devishvili (magnetism, inelastic scattering)
  • Max Wolff (polymers, solid/liquid interfaces, ionic liquids, quasi-elastic scattering)

You can also consult the proposal writing guidelines at the ILL.

The figure shows the instrument in the high flux configuration. This configuration is good for experiments that do not require polarization or high resolution. Examples are solid/liquid interfaces and hydrogen in thin films.

Instrumentation Details

The instrument has two modes of operation: a low resolution − high flux and one high resolution mode. Currently we only use the high resolution mode which is mainly used for polarized neutron reflectivity.

  • All the material that are published using data from Super Adam has to acknowledge VR for the financial support for funding Super Adam.
  • The part of the Super Adam team that has been involved in the measurements shall be included as an author of the published material. This is due to that when we give support, to the extent desired by the user, we will engage full in the task at hand.
  • All publications has to follow the Vancouver rules of conduct. (see e.g. http://www.icmje.org/index.html and http://www.codex.vr.se/en/etik2.shtml)

User Rules

Authorship credit should be based on:

  1. Substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data
  2. Drafting the article or revising it critically for important intellectual content and
  3. Final approval of the version to be published.

Authors should meet conditions 1, 2, and 3. (from the Vancouver-rules on authorship)

Contact

The principal investigator: Björgvin Hjörvarsson

Co-applicants: Max Wolff, Jens Birch (Linköping University) and Tommy Nylander (Lund University).

Alexei Vorobiev, Responsible for Super ADAM at ILL
Postal address: Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, F-38042 Grenoble Cedex 9
Email: alexey.vorobiev@physics.uu.se, avoroviev@ill.eu
Tel: +33 476 20 7289

Gunnar Pálsson, Assistant professor in Neutron reflectometry and modern materials science
Postal address: Room 61411 Ångströmlaboratoriet, Box 516, Lägerhyddsvägen 1, 75120 Uppsala
Email: Gunnar.Palsson@physics.uu.se
Tel: +46(0)184713556

Ion beams are used for analysis of materials, ranging from archeology and medicine to ultra thin surface coatings in optics or electronics and other applications. Our accelerators can also be used to actively change the properties of materials, or to structure samples at nanometer level. Fundamental research is carried out in the whole field, in order to meet future demands in the development and analysis of materials.

Read more about Ion Physics

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