ABSTRACT
In-plane microwave penetration depth lambda_{ab} and quasiparticle conductivity at 28 GHz are measured in underdoped single crystals of the Fe-based superconductor PrFeAsO_{1-y} (T_{c} approximately 35 K) by using a sensitive superconducting cavity resonator. lambda_{ab}(T) shows flat dependence at low temperatures, which is incompatible with the presence of nodes in the superconducting gap Delta(k). The temperature dependence of the superfluid density demonstrates that the gap is nonzero (Delta/k_{B}T_{c} greater, similar1.6) all over the Fermi surface. The microwave conductivity below T_{c} exhibits an enhancement larger than the coherence peak, reminiscent of high-T_{c} cuprate superconductors.
ABSTRACT
Giant negative thermal expansion is achieved in antiperovskite manganese nitrides when the sharp volume change associated with magnetic ordering is broadened by substitution. In this Letter, we address the unique role of the ''magic" element, Ge, for such broadening in Mn3Cu1-xGexN. We present evidence for a local lattice distortion well described by the low-temperature tetragonal (T4) structure of Mn3GeN for a range of x, where the overall structure remains cubic. This structural instability shows a strong correlation with the broadness of the growth of the ordered magnetic moment and, hence, is considered to trigger the broadening of the volume change.
ABSTRACT
Suspended Si(3)N(4) nanosheets at least 4 µm in width and ranging from 1.5 to 4 nm in thickness were successfully synthesized for the first time. Several of those nanosheets had scrolled edges due to being ultra-thin. According to transmission electron microscopy (TEM) and atomic force microscopy (AFM) observations, the Si(3)N(4) nanosheets exhibit microscopic corrugations in the range of several tens of nanometres. In addition, the directions of the microscopic corrugations were not random, but instead parallel to specific crystal orientations.
