You are here

Highlights

  • For the first time, researchers can now both explain and predict the behavior of different materials while they are being pulled apart.  Some materials are ductile, meaning they will deform without losing their toughness, and others are brittle.  The results explain even the unexpected ductility of a material within a class of rare-earth-containing materials that are otherwise known to be brittle.  To predict the behavior requires two maps.  The first map reveals whether a system has the ability to slip in a particular direction and form stable...

    Read More
  • A distinct anomaly exists within a series of iron arsenic superconductors, possibly indicating a new form of iron-based superconductivity. This is seen in plots of the temperature at which the material becomes superconducting (Tc) compared to the change in heat capacity at the superconducting temperature.(Heat capacity is the amount of heat needed to raise the temperature of a material by one degree.)Typically, newly discovered Fe-base superconductors follow a simple empirical rule:the change in the sample’s heat capacity when it becomes superconducting varies with the cube of...

    Read More
  • Researchers have discovered a new family of stable quasicrystals made from only two elements, a rare earth and cadmium. The family includes the first magnetic binary quasicrystals. Quasicrystals are metallic alloys that lack the periodic order seen in conventional crystals. Instead, they exhibit aperiodic, long-range order and have “forbidden” rotational symmetries (for example, five-fold). Most are made from three or four elementsBinary quasicrystals are rare and sought by scientists because they offer a cleaner way to investigate the relationships between the unusual structures of...

    Read More
  • Nanoscale twin boundaries — where one side of the boundary is a mirror image of the other — are not straight as thought, but instead have "kinks". Researchers used a newly developed transmission electron microscopy technique to resolve the orientation of features along these boundaries with 1 nanometer resolution. Twin boundaries that appear straight at lower resolution, actually contain many kink-like steps. These kinks are distributed non-uniformly from twin boundary to twin boundary. By correlating the new results and additional experiments with large-scale simulations, researchers...

    Read More
  • Researchers have discovered that barium–iron–nickel–arsenic superconductors clearly deviate from the famous Ginzburg-Landau Theory developed in the 1960’s. According to this theory, superconductors should show a linear relationship between the magnetic field at which superconductivity is suppressed (known as the upper critical field) and the direction of the magnetic field. Using single crystals, researchers performed detailed experiments of the upper critical field as a function of temperature and the direction of the magnetic field. They were able to study the dependence on magnetic...

    Read More
  • Physicists have devised a material that allows them to study the birth and evolution of magnetism.  This is analogous to understanding how a caterpillar becomes a butterfly.  Without understanding the key transitional point in its lifecycle, a butterfly just seems to appear fully formed.   For butterflies, we need to discover and study a chrysalis.  Taking this cue from nature, scientists have developed ytterbium—bismuth—platinum (YbBiPt) and used a magnetic field to suppress a non-magnetic, metallic...
    Read More
  • Physicists have devised a material that allows them to study the birth and evolution of magnetism.  This is analogous to understanding how a caterpillar becomes a butterfly.  Without understanding the key transitional point in its lifecycle, a butterfly just seems to appear fully formed.   For butterflies, we need to discover and study a chrysalis.  Taking this cue from nature, scientists have developed ytterbium—bismuth—platinum (YbBiPt) and used a magnetic field to suppress a non-magnetic, metallic state and study how a non‐magnetic metal develops magnetic...

    Read More
  • Researchers have discovered an unusual temperature behavior of the electrons in iron arsenic superconductors that may play a crucial role in the emergence of high temperature superconductivity. The electrons in solids occupy areas called pockets. In regular metals the sizes of these pockets remain constant as a function of temperature and are proportional to number of electrons that conduct current. Surprisingly, in iron arsenic high temperature superconductors, the pocket associated with empty electron states, known as holes, decreases and ones associated with electrons expand, as if...

    Read More
  • A new material made from three elements — yttrium, manganese and gold — woven together in an unusual crystalline lattice shows surprisingly diverse characteristics for each element. The manganese electrons are localized at the manganese sites, whereas the yttrium and gold electrons are delocalized. Yttrium in this rhombohedral lattice tends to give up electrons and thus be positively charged whereas the gold prefers to take on electrons. The magnetic characteristics are also unusual with electron spins strongly aligned only at the manganese sites. This research is an excellent...

    Read More
  • How current flows through iron-based superconductors is very sensitive to composition.  Iron-based superconductors provide a unique window into the role magnetism plays in superconductivity, because their magnetism and superconductivity coexist, whereas in conventional superconductors they do not.  Researchers studied current flow by measuring the resistivity along various directions of barium–potassium–iron–arsenide superconductors with differing amounts of potassium.  Samples with lower amounts of potassium exhibit electric current flow that is easier in one direction,...

    Read More

Pages