C. L. Dong | Searcharxiv

arXiv2010

Influence of itinerancy on the magnetic properties of the single crystals of Sr2YRu1-xCuxO6 solid solutions

X-ray absorption spectroscopy(XAS) Ru L-edge and O K-edge measurements on single crystals of Sr2YRu1-xCuxO6 (x=0.01-0.05) solid solutions show that Cu replaces Ru in the lattice which results in a lattice distortion and itinerant holes that increase with increasing x. Powder X-ray diffraction (XRD) measurements confirm the lattice distortion through changes in the lattice parameters. Magnetic measurements reveal an antiferromagnetic transition at 32 K in the crystals with x=0 and a diamagnetic transition at 32 K for x \geq 0.01indicative of superconductivity in the zero field cooled (ZFC) curves. The field cooled (FC) curves show a weak ferromagnetic character with x=0 and a ferromagnetic transition at 30 K and an antiferromagnetic transition at 23 K in the presence of Cu. The peak at 30 K in the ac susceptibility measurements indicates a spin-glass behavior. The low field part of the M-H curve for x=0.05 crystal indicates weak superconductivity. The shifting of the M-H curve on FC indicates spin-glass state. In conjunction with the XAS results the magnetic behavior is explained in terms of a spontaneous vortex state as a result of the non-freezing Ru5+ spins.

cond-mat.supr-con↗

arXiv2010

X-ray absorption spectroscopy (XAS) investigation of the electronic structure of superconducting FeSex single crystals

X-ray absorption spectroscopy (XAS) Fe K-edge spectra of the FeSex (x=1-0.8) single crystals cleaved in situ in vacuum reveal characteristic Fe 4sp states, a lattice distortion and the Se K-edge spectra point to a strong Fe 3d-Se 4p hybridization giving rise to itinerant charge carriers. A formal charge of ~1.8+ for Fe and ~2.2- for Se were evaluated from these spectra in the FeSex (x=0.88). The charge balance between Fe and Se is assigned itinerant electrons located in the Fe-Se hybridization bond. As x decreases the 4p hole count increases and a crystal structure distortion is observed that in turn causes the Fe separation in the ab plane change from 4p orbital to varying (modulating) coordination. Powder x-ray diffraction (XRD) measurements also show a slight increase in lattice parameters as x decreases (increasing Se deficiency).

cond-mat.str-el↗