Inorganic chemistry synthesis

    • With newly developed synthesis techniques, new fields of chemistry are available. Solid-state syntheses under normal and inert conditions at high and low pressures are the most commonly used methods, but it has become important to find new routes to produce either purer compounds or larger single crystals. Also, meta-stable phases and low temperature phases might only be assessable by "tricking" thermodynamics. The trick is often the introduction of a catalyst or an additive to increase the reactivity of the constituents. This enables a low-temperature reaction below the problematic decomposition of the product. In inorganic chemistry, this additive is called solvent or flux and should consist of something that partly solves the reactants but does not turn up as inclusion in the final product. Low melting metals, e.g. Ga, Sn, and Bi, as well as salts or salt mixtures with low eutectic melting temperatures, e.g. alkali metal halides, can be used. The metal melts are often used for intermetallics while the salt melts can be use for a wide range of compounds due to the relative stability against redox reactions. A more recent development is the use of ionic liquids that can be described as a solvent of dipolar molecules, similar to water, but with much higher chemically stability. Even more exotic solvents are condensed gases of for example NH3 which allow reactions under extremely reducing conditions but with solubility of, usually very electropositive, metals. The reactions in condensed gases are performed at very low temperatures (far below the freezing of water). On the other side, in high temperature reactions it is important to avoid, if possible, a sample holder or to chose its material so that it does not react with the sample. Extreme temperatures can be reached with either high frequency-, optical-, or arc-melting furnaces. With the former it is even possible to let the reaction happen while floating in vacuum or inert gas. The optical furnace allows for local heating (laser or focused light) that makes is possible to use the sample itself as sample holder and, thus, avoiding the use of a sample holder. There are even more interesting developments in this field the last decades and I expect that many new materials will appear in the near future due to the emerging techniques.

    Crystal stuctures

    • We have to accept that Nature selects the way a crystal structure is built from a certain composition of elements. However, there are several situations where the outcome is really difficult to understand. These are for example modulated structures that need super-space description, i.e. beyond 3D space, and the quasi crystals that seem to break the accepted rules of periodicity by signaling 5-, 7-, or 10-fold symmetry axes. I follow this research field with great interest and contribute to it, every time the chance is given.
      The presence of an electric polarity in a crystal structure has to come at the cost of something. This is why the centrosymmetric crystals are more common in nature. Consequently, this increases the interest of the non-centrosymmetric systems in search of the whereabouts of the spent energy. Further, the structural polarity in magnetic insulator allows for rare physical properties to appear, such as the coupling between magnetic and electric ordering phenomena, often mentioned as multiferroidicity. Here, I see a gain in fundamental knowledge by identifying more such systems and reporting on their basic properties. With an increasing library of multiferroic compounds, it will be possible to draw general conclusions on the appearance of magnetoelectric couplings.

    Magnetism

    • The diversity of this physical property has intrigued me already a long time and there are many magnetic aspects that need further understanding. Hence, by looking for new compounds with unusual topology and dimensionality of magnetic ions with different spin sizes, I want to contribute to the field of magnetism. Naturally, the most well-known long range spin ordering phenomena are interesting, but also the possible reasons for not having them. The most prominent phenomenon connected to the suppression of magnetic ordering is found within the geometry of the magnetic lattice, i.e. the symmetry and relative positions of magnetic ions. These system are often called frustrated, because they cannot order although the spin-spin interactions are stronger that the surrounding temperature. This frustration is a result of competing spin-spin interactions, leaving the spin system with no other choice than to stay disordered. These "spin-liquids" behave extra ordinary at low temperatures where quantum fluctuations (statistical distribution of energetically slightly different or degenerate states) start to play a role.
      Magnetism might also have a correlation to the electric polarity and/or crystal field from the crystal structure (see above). Spins affected by the electric polarity gain extra degrees of freedom an might form exotic state like helimagnets, chiral magnets, or canted antiferromagnets.
      We all know that magnetism is a strong part of technical everyday life and every new discovery might have a great influence on our civilization.

    Relativity

    • Although this topic seems far from the others above, it is a topic that is keeping my mind busy. There are several famous names attached to this effect and no one has been able to deliver a model or function to even convince a large majority of natural scientists today. Despite this, several effects are said to be connected to relativity, even the low melting point of mercury. That there is a connection between relativity, gravity, and the speed of light is commonly accepted but to what extent does this hold in a general view? Still, this puzzle will be the most intriguing one to solve - if anyone succeeds at all.