We infer that soft-x-ray absorption spectroscopy is a versatile method for the determination of the crystal-field ground state symmetry of rare earth heavy fermion systems, complementing neutron scattering. Using realistic and universal parameters, we provide a theoretical mapping between the polarization dependence of Ce M(4,5) spectra and the charge distribution of the Ce 4f states. The experimental resolution can be orders of magnitude larger than the 4f crystal-field splitting itself. To demonstrate the experimental feasibility of the method, we investigated CePd2Si2, thereby settling an existing disagreement about its crystal-field ground state.

Electromagnetic and electrostatic levitation are applied to undercool melts of pure Zr. Each sample is undercooled approximately 100 times and the distribution functions of undercoolings are determined. They are analyzed within a statistical approach of classical nucleation theory. Despite large undercoolings the analysis predicts heterogeneous nucleation in electromagnetic levitation. Electrostatic levitation leads to an increase of average undercooling and the statistical analysis indicates that the undercoolings approach the limit as given by homogeneous nucleation.Crystallization of liquids is a first-order phase transition and initiated by nucleation. The activation barrier of nucleation controls the undercooling level measured in experiments. One distinguishes between heterogeneous nucleation and homogeneous nucleation. Heterogeneous nucleation is an extrinsic process in which container walls and/or foreign phases in the melt participate in. In contrast homogeneous nucleation is an intrinsic process, in which the undercooled liquid and the solid nucleus are involved. Hence, heterogeneous nucleation is governed by the experimental conditions whereas homogeneous nucleation depends on the properties of the system investigated.In the present work we apply electromagnetic ͑EML͒ and electrostatic levitation ͑ESL͒ techniques to investigate the maximum undercooling of pure Zr. Using these containerless processing methods heterogeneous nucleation on container walls is completely circumvented. Samples were processed by about 100 heating and cooling cycles in both experimental setups. The probability distribution of undercoolings measured in both levitators are analyzed within a model of Skripov. 1 The evaluation of the undercooling distribution functions yields the activation energy of crystal nucleation and the density of nucleation sites. Both quantities were found to be different for EML and ESL experiments. The results are discussed with respect to the physical nature of nucleation observed in both different sets of experiments.Sphere like Zirconium samples were prepared from ingot material purchased from Teledyne Wah Chang with a purity of 99.995% cut into pieces and melted in an arc furnace made of UHV compatible stainless steel components under high purity Ar gas ͑6N͒. For EML ͑Ref. 2͒ the samples of 8 mm in diameter are processed in an ultrahigh vacuum chamber, which is evacuated to a pressure of 10 −7 mbar before backfilling with He gas with a purity of 6N. The compensation of the gravitational force implies a minimum power absorption to levitate the sample. Heat radiation is not sufficient to transfer the heat produced in the electromagnetically levitated sample and to cool it below its melting temperature. Therefore, cooling by forced convection with He of high purity is used to cool the sample. For ESL, 3 samples of 2 mm in diameter are processed under ultra high vacuum conditions ͑Ϸ2 ϫ 10 −8 mbar͒. Levitation and heating is decoupled in contrast to EML. In both levitation setups the temperature is measur...

The atomic structures in equilibrium and supercooled liquids of Zr 80 Pt 20 were determined as a function of temperature by in-situ high-energy synchrotron diffraction studies of the levitated liquids (containerless processing) using the beamline electrostatic levitation (BESL) technique. The presence of a pronounced pre-peak at q ~ 1.7 Å -1 in the static structure factor indicates medium range order (MRO) in the liquid. The position and intensity of the pre-peak remain constant with cooling, indicating that the MRO is already present in the liquid above its melting temperature. An analysis of the liquid atomic structures obtained using the Reverse Monte Carlo (RMC) method utilizing both the structure factor, S(q), from x-ray diffraction experiments and the partial pair-correlation functions from ab initio molecular dynamics (MD) simulations show that the pre-peak arises from a Pt-Pt correlation that can be indentified with icosahedral short-range order around the Pt atoms. The local atomic ordering is dominated by icosahedral-like structures, raising the nucleation barrier between the liquid and these phases, thus assisting glass formation.

Sr3(Ru(1-x)Mnx)2O7, in which 4d-Ru is substituted by the more localized 3d-Mn, is studied by x-ray dichroism and spin-resolved density functional theory. We find that Mn impurities do not exhibit the same 4+ valence of Ru, but act as 3+ acceptors; the extra eg electron occupies the in-plane 3d(x2-y2) orbital instead of the expected out-of-plane 3d(3z2-r2). We propose that the 3d-4d interplay, via the ligand oxygen orbitals, is responsible for this crystal-field level inversion and the material's transition to an antiferromagnetic, possibly orbitally ordered, low-temperature state.