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Under Pressure - A Material's Secrets Revealed

Researchers have used pressure as a tool to study the magnetic behavior of a challenging series of materials, RVSb3, where R is a rare-earth.  This series offers a way to study magnetic ordering in materials with a single, unique rare-earth site and it has been studied primarily as a function of temperature. CeVSb3 is the only compound in the family that orders ferromagnetically, that is with all its unpaired electron spins parallel, at low temperatures.

Seeing Order Emerge out of Chaos

Using computer simulations, researchers are able to watch how a random mixture of gold nanoparticles with two different DNA strands as linkers assemble right on their computer screen. The magic starts with just a fraction of the nanoparticles forming a large cluster like a plate of spaghetti and meatballs. Within this random cluster, small ordered regions form and eventually lock together into a large uniform array of particles held together with DNA strands. Using computer simulations they also predict previously unseen structures.

OOPS! That Funny Behavior is Just an Accident, Really.

Iron and copper are both magnetic, but only iron sticks to your refrigerator. That’s because iron is ferromagnetic at room temperature, while copper is paramagnetic. For a material to have two types of magnetism simultaneously at one temperature is uncommon. To have three types simultaneously is exceedingly rare. The alloy NbFe2 is one of those rare materials: at low temperatures it is ferromagnetic, paramagnetic and antiferromagnetic.But why?

Toss in a Little Ruthenium, Apply Pressure and Voilà!

Researchers working to understand high temperature superconductivity in barium-iron-arsenide have discovered that applying pressure affects the material's magnetic and superconducting behavior just as if they had replaced some iron with a little ruthenium. To better quantify and understand the similarities of changing pressure versus ruthenium concentration, they made Ba(Fe1-xRux)2As2 with varying amounts (x) of ruthenium and studied each concentration as a function of pressure and temperature.

Rounding Corners to Make Superconductors Work Better

Making superconducting nanocircuits with rounded internal corners will significantly improve performance.Scientists showed this by calculating how circuit geometry impacts current flow. The key is how geometry affects “current crowding”. Crowding can happen when electrical current travels around a sharp corner or hairpin turn much like cars racing on a tight track. The current (like cars) tends to concentrate near the inner edges of sharp turns.

Expulsion Leads to a New Catalyst

Locating a catalyst and reactants in confined spaces makes catalytic reactions go faster in the desired direction. Of course, the reaction products have to be removed from the confined spaces and researchers have developed a new approach to expelling aqueous reaction products. This works for confinement in nanometer-sized pores in silica particles. By lining the insides of the pores with both catalysts and a fluorinated chemical, like that found in Teflon®, reactions with water as a byproduct proceed much faster. This works because certain chemicals just don’t like each other.

Peculiar Magnetic Microstructure Pilots Badwater Bacteria

A new group of bacteria has been discovered in Death Valley’s Badwater Basin that makes nanoparticles of both magnetite (Fe3O4) and greigite (Fe3S4). Magnetotactic bacteria use these tiny magnets as part of their navigation system to align themselves along the Earth’s magnetic field. Typical magnetotactic bacteria do not make both magnetite and greigite and the discovery dispels the notion that greigite-producing bacteria live only in marine environments.

Untangling what Controls Superconductivity

Substituting ruthenium for iron in iron-based superconductors tunes their properties in a very unusual way. The substitution of one element for another normally changes the crystal’s electronic structure and induces superconductivity by adding charge carriers and/or altering the size of the crystal lattice. High resolution angle-resolved photoemission experiments showed neither mechanism is responsible in the case of barium–iron–ruthenium–arsenide, Ba(Fe1-xRux)2As2.

Ultrafast Moves — Caterpillar Style

A layer of lead on clean silicon moves in a surprising way — in waves like a caterpillar. This explains the unexpected ultrafast mass transport observed even at low temperatures for this system. Although solid these single layers of atoms move as fast as molten lead. Computer simulations show that the lead layer forms waves that require almost no energy to keep moving thus explaining the quickness of mass transport. Other metals on surfaces typically move much slower by one atom at a time hopping along the surface.


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