Magnetic correlations near the magnetostructural phase transition in the bilayer iron-pnictide parent compound, BaFe2As2, are measured. In close proximity to the antiferromagnetic phase transition in BaFe2As2, a crossover to three-dimensional critical behavior is anticipated and has been preliminarily observed. Here we report complementary measurements of two-dimensional magnetic fluctuations over a broad temperature range about TN. The potential

We report electronic density of states measurements of oxygen vacated PrFeAsO using soft X-ray absorption and emission spectroscopy. The electronic density of states is observed to undergo doping dependent shifts. Oxygen X-ray absorption and emission show long-range intermixing of oxygen p states. Mean field theory and local density approximations give a good description of the measured oxygen and iron spectra. The near Fermi-level iron spectral

Measurements of the upper critical field Hc2 near Tc of Pr1-xLaxOs4Sb12 were performed by specific heat. The results support the hypothesis of a non-single-ion origin of m* enhancement in PrOs4Sb12, derived from the analysis of the C/T discontinuity at Tc. Both sets of measurements indicate the existence of a crossover concentration, xcr~0.2–0.3, separating heavy fermion-like alloys (x < xcr) from normal metals (x > xcr). Heavy fermion-like alloys

The electronic specific heat of PrOs4Sb12 was measured on different single crystals at temperatures down to 40 mK using a relaxation method. All investigated crystals exhibited a broad shoulder in specific heat near 0.4 K. This anomaly seems to be related to that found previously in Sb nuclear quadrupolar resonance study and possibly in lower critical-field and penetration-depth measurements. The onset of the specific-heat anomaly shows no response

Commonalities among the order parameters of the ubiquitous antiferromagnetism present in the parent compounds of the iron arsenide high-temperature superconductors are explored. Additionally, comparison is made between the well established two-dimensional Heisenberg-Ising magnet, K2NiF4 , and iron arsenide systems residing at a critical point whose structural and magnetic phase transitions coincide. In particular, analysis is presented regarding

The electronic phase diagram of PrFeAsO_{1-x}F_{x} (0

Using angle-integrated photoemission spectroscopy we have probed the novel LaFeAsO0.9F0.1 superconductor over a wide range of photon energies and temperatures. We have provided a full characterization of the orbital character of the valence-band (VB) density of states (DOS) and of the magnitude of the d-p hybridization energy. Finally, we have identified two characteristic temperatures: 90 K where a pseudogap-like feature appears to close and 120

The resistivity and magnetoresistance of La-doped CeOs4Sb12 and PrOs4Sb12 were investigated at temperatures down to 20 mK and in magnetic fields up to 18 T. The resistivity of Ce0.98La0.02Os4Sb12, in fields smaller than 4 T, has a Kondo-hole impurity temperature variation, i.e., ρ=ρ0+AT2, with a negative and strongly field-dependent A. However, the positive magnetoresistance suggests that this anomalous behavior is due to Kondo-hole bands. The