You are here

Highlights

  • Cover featuring an image from Petit et al. The figure shows the 3D Fermi surface for a paramagnetic compound of gadolinium and magnesium.

    Theoretical modeling has led to a key development in our understanding of the deeply complex magnetic properties in a series of rare-earth intermetallic materials.  Rare-earth elements are unique in that their cores hold strongly localized electrons that underpin their novel magnetic properties.  When combined with transition metals, rare earths become technologically-useful intermetallic materials.  Here gadolinium—an element from the middle of the rare earth series—and either magnesium, zinc, or cadmium was combined to create the materials.  Researchers developed a theory explaining how...

    Read More
  • Shown is the temperature dependence of the band dispersion at the hole pocket divided by the Fermi function.  Researchers found that upon increase of the temperature the electron pockets remain intact, while the hole pockets vanished above 165 K. The pink arrow points to a band located above the hole band.

    For the first time, a temperature-driven contour change in an electron behavioral map—known as the Fermi surface—has been reported.  The key properties of conducting materials are determined by the behavior of the electrons that reside on so called “Fermi surface.”  Changes in the shape of this surface, known as Lifshitz transitions, previously were seen only when substantial pressure was applied or the chemical composition of the material was modified.  Employing a technique that uses light energy (photons) to study electron properties within a sample, known as angle-resolved...

    Read More
  • Extensive calculations revealed that the calcium-iridium-oxygen compound CaIrO3 is a Slater-type insulator, putting to rest the debate of whether the insulating nature of the metal oxide is Mott-type or Slater-type.  While both types are insulators, the insulating properties in Mott types arise from electron repulsion while in Slater types magnetic ordering plays a prominent role.  Through a series of calculations, the team described the types of interactions between the various atoms in the oxide.  Their calculations took temperature into consideration, because it is known...

    Read More
  • A compound made out of ytterbium (Yb), platinum (Pt), and bismuth (Bi) offers researchers the opportunity to watch the birth of magnetic behavior by applying small changes in magnetic field or temperature.  Despite the electrons having effective masses of nearly 10,000 times their normal mass when YbPtBi becomes magnetic, researchers have been able to monitor its quantum oscillations, key for determining important electronic properties.  From the results they deduced that as it moves further and further from magnetism its electrons lose weight fast.  These findings provide key...

    Read More
  • Two types of magnetic configurations—antiferromagnetism (AFM) and ferromagnetism (FM)—have been found to compete with each other, thwarting the rise of superconductivity in iron pnictides, a class of high-temperature superconductors.  In an AFM fluctuation electron spins temporary align in an alternating checkboard pattern while electron spins align temporary in the same direction in a FM fluctuation.  While FM fluctuations have been suggested in the iron pnictide superconductors by theoretical calculations, the possible existence of FM fluctuations has not yet been examined from a...

    Read More
  • Oxygen is one of the most ubiquitous elements in chemistry and materials science, yet one of the most elusive elements for spectroscopic investigation by solid-state Nuclear Magnetic Resonance (SSNMR). Used to determine the structure of materials and chemicals on the atomic scale, SSNMR requires nuclei that have magnetic moments. Yet, less than four of every 10,000 oxygen nuclei are 17O, the only NMR-active isotope of oxygen. Detecting the elusive oxygen isotope now has become a reality thanks to unprecedented advancement in SSNMR, referred to as Dynamic Nuclear Polarization (...

    Read More
  • Two distinct types of magnetism aligned perpendicular in a single crystal have been detailed in new measurements on single-crystal and powered samples composed of barium, potassium, manganese, and arsenic.  Antiferromagnetism occurs with a checkerboard-style patterning of the total atomic magnetic moments due to the spins of the localized electrons of the manganese atoms (known as ‘local-moment magnetism’).  Aligning perpendicular to the antiferromagnetic order, ferromagnetism (where all electron spins point in the same direction) also occurs, but is assigned specifically to the mobile...

    Read More
  • Swapping out hard-shelled nanoparticle models for the soft-shelled variety has led to theoretical results in tune with experimental findings for building supercrystal nano materials. These are fundamental new type of material that are built from nanoparticles displaying long range order. In the process of building, the nanoparticles interact, jockeying for position in the lattice. Whereas models of hard-shelled nanoparticles only clink against each other, the flexible exterior of soft-shelled nanoparticles makes their interactions much more complex. By using two soft-shelled nanoparticles...

    Read More
  • A novel ultrafast terahertz probe has traced dark composite particles and confirmed, for the first time, that their formation occurs on the femtosecond timescale in single-walled carbon nanotubes. Dark particles, known as dark excitons, are composite pairs of quasielectrons and electron holes. Single-walled carbon nanotubes have unique electrical properties governed by the presence of dark and bright particles. Because dark excitons cannot emit a photon like their bright counterparts, they do not interact with visible light, rendering them difficult to trace. Researchers instead used...

    Read More
  • Tunable near-UV microcavity organic light-emitting diodes (OLEDs) that emit in the deep blue and ultraviolet light region have been developed using a novel approach. These devices address the growing need for portable compact near-UV sources for analytical tools as well as various biomedical and forensic applications. These are among the first OLEDs that emit in the near-UV region. In this new approach, the team tuned the thickness of the spacer layer of a nanometer wide microcavity, allowing them to tailor each individual OLED in the array to the desired narrow-band emission. Simulations...

    Read More

Pages