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.
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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.
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.
A new technique makes it possible to track not only the location of moving particles to within 10 nanometers, but also their rotation and orientation. This is like watching a football game from the ionosphere and knowing where the football is at anytime within 1.5 inches, how the ball is spinning, and what direction it is moving.
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.
For the first time, researchers can keep multiple nanoparticles in focus while tracking their 3D orientations on a surface with unprecedented angular resolution. The new technique can accurately track anisotropic gold particles that are tilted out of the horizontal plane and has the advantage of not relying on particle interactions with the surface to keep track of them.
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.
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).
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.
A distinct anomaly exists within a series of iron arsenic superconductors, possibly indicating a new form of iron-based superconductivity.