Pressure-tuned spin and charge ordering in an itinerant antiferromagnet

Elemental chromium orders antiferromagnetically near room temperature, but the ordering temperature can be driven to zero by applying large pressures. We combine diamond anvil cell and synchrotron x-ray diffraction techniques to measure directly the spin and charge order in the pure metal at the approach to its quantum critical point. Both spin and charge order are suppressed exponentially with pressure, well beyond the region where disorder cuts off such a simple evolution, and they maintain a harmonic scaling relationship over decades in scattering intensity. By comparing the development of the order parameter with that of the magnetic wave vector, it is possible to ascribe the destruction of antiferromagnetism to the growth in electron kinetic energy relative to the underlying magnetic exchange interaction

Reactivity of He with ionic compounds under high pressure

Helium was long thought to be unable to form stable solid compounds, until a recent discovery that helium reacts with sodium at high pressure. Here, the authors demonstrate the driving force for helium reactivity, showing that it can form new compounds under pressure without forming any local chemical bonds

High pressure synthesis and study of low-compressibility molybdenum nitride (MoN and MoN1-x) phases

We report the compressibility of the stoichiometric hexagonal delta phase of MoN that is a well-known hard material that becomes superconducting below T-c=12 K. The measured bulk modulus is K-0=345(9) GPa and K'(0)=3.5(3). We also report the compressibility of the non-stoichiometric cubic B1 structured gamma-Mo2N phase, that has a lower bulk modulus [K-0=301(7) GPa, assuming K'(0)=4]. The difference in bulk modulus is due to the difference in structure and the cohesive energy between the two phases