The local magnetic and electronic structures of chromium substituted iron oxide polycrystalline samples are investigated via Fe L-edge x-ray absorption near-edge structural and magnetic circular dichroism measurements...The local magnetic and electronic structures of chromium substituted iron oxide polycrystalline samples are investigated via Fe L-edge x-ray absorption near-edge structural and magnetic circular dichroism measurements.A strong dependence of atomic magnetic levels on the applied external magnetic field is observed.The magnetic behavior of Cr-doped iron oxides are determined to be dominantly governed by the d-d hybridization between Fe and Cr valence levels.In addition,the formation of CrO_(2) and Cr_(2)O_(3) chromium oxide clusters in the sample are observed to determine the magnetic ordering,i.e.anti-ferromagnetic or ferromagnetic with the changing external magnetic fields.The results highly agree with the previous studies.展开更多
Employing the angle-resolved photoemission spectroscopy, we study the electronic structure of TaFe1.23Te3, a two-leg spin ladder compound with a novel antiferromagnetic ground state. Quasi-two-dimensional （2D） Fermi...Employing the angle-resolved photoemission spectroscopy, we study the electronic structure of TaFe1.23Te3, a two-leg spin ladder compound with a novel antiferromagnetic ground state. Quasi-two-dimensional （2D） Fermi surface is observed, with sizable inter-ladder hopping. Moreover, instead of observing an energy gap at the Fermi surface in the antiferromagnetic state, we observe the shifts of various bands. Combining these observations with density-functional-theory calculations, we propose that the large scale reconstruction of the electronic structure, caused by the interactions between the coexisting itinerant electrons and local moments, is most likely the driving force of the magnetic transition. Thus TaFe1.23Te3 serves as a simpler platform that contains similar ingredients to the parent compounds of iron-based superconductors.展开更多
The electronic structures of Ni-Ti shape-memory alloy samples were investigated by X-ray absorption fine structure （XAFS） spectroscopy both experimentally and theoretically. In the experimental section, the samples ...The electronic structures of Ni-Ti shape-memory alloy samples were investigated by X-ray absorption fine structure （XAFS） spectroscopy both experimentally and theoretically. In the experimental section, the samples were measured at low temperature to determine the persistent traces of both preheating process and atomic concentration effects on the crystal and electronic structure by X-ray absorption near-edge structure （XANES） spectroscopy. As a second step, the extended-X-ray absorption fine structure （EXAFS） calculations, which are based on different choices of one electron potentials according to Ti coordinations by using the real space multiple scattering method FEFF 8.2 code, were performed. The crystallographic and electronic structures of the porous Ni-Ti alloys were tested at various temperatures ranging from 5 to 1323 K.展开更多
The newly discovered iron-chalcogenide superconductorKxFe2ySe2exhibits a distinct electronic structure from other iron-based superconductors.Exploiting polarization-dependent angle-resolved photoemission spectroscopy,...The newly discovered iron-chalcogenide superconductorKxFe2ySe2exhibits a distinct electronic structure from other iron-based superconductors.Exploiting polarization-dependent angle-resolved photoemission spectroscopy,we have determined the orbital characters of band structure in aKxFe2ySe2superconductor.To a large extent,we find thatKxFe2ySe2superconductor shares similar orbital characters with other iron-based superconductors,but with its own characteristics.For example,we have resolved two highly degenerate electron cylinders around the zone corner in the s and p geometries,respectively,indicating negligible interactions between them.Moreover,in contrast to the band calculation results,the small electron pocket around Z is found to be mainly consisted of the d z 2 orbital.The determined orbital characters would help to construct a realistic model forKxFe2ySe2.展开更多
文摘The local magnetic and electronic structures of chromium substituted iron oxide polycrystalline samples are investigated via Fe L-edge x-ray absorption near-edge structural and magnetic circular dichroism measurements.A strong dependence of atomic magnetic levels on the applied external magnetic field is observed.The magnetic behavior of Cr-doped iron oxides are determined to be dominantly governed by the d-d hybridization between Fe and Cr valence levels.In addition,the formation of CrO_(2) and Cr_(2)O_(3) chromium oxide clusters in the sample are observed to determine the magnetic ordering,i.e.anti-ferromagnetic or ferromagnetic with the changing external magnetic fields.The results highly agree with the previous studies.
基金Supported by the National Basic Research Program of China under Grant Nos 2012CB921400,2011CB921802 and 2011CBA00112
文摘Employing the angle-resolved photoemission spectroscopy, we study the electronic structure of TaFe1.23Te3, a two-leg spin ladder compound with a novel antiferromagnetic ground state. Quasi-two-dimensional （2D） Fermi surface is observed, with sizable inter-ladder hopping. Moreover, instead of observing an energy gap at the Fermi surface in the antiferromagnetic state, we observe the shifts of various bands. Combining these observations with density-functional-theory calculations, we propose that the large scale reconstruction of the electronic structure, caused by the interactions between the coexisting itinerant electrons and local moments, is most likely the driving force of the magnetic transition. Thus TaFe1.23Te3 serves as a simpler platform that contains similar ingredients to the parent compounds of iron-based superconductors.
基金partly supported by BIDEB-2219 grant of TUBITAK,Turkey and ADYUBAP,Turkey
文摘The electronic structures of Ni-Ti shape-memory alloy samples were investigated by X-ray absorption fine structure （XAFS） spectroscopy both experimentally and theoretically. In the experimental section, the samples were measured at low temperature to determine the persistent traces of both preheating process and atomic concentration effects on the crystal and electronic structure by X-ray absorption near-edge structure （XANES） spectroscopy. As a second step, the extended-X-ray absorption fine structure （EXAFS） calculations, which are based on different choices of one electron potentials according to Ti coordinations by using the real space multiple scattering method FEFF 8.2 code, were performed. The crystallographic and electronic structures of the porous Ni-Ti alloys were tested at various temperatures ranging from 5 to 1323 K.
基金supported in part by the National Natural Science Foundation of China,Ministry of Education of Chinathe National Basic Research Program of China (2012CB921400,2011CB921802 and 2011CBA00112)
文摘The newly discovered iron-chalcogenide superconductorKxFe2ySe2exhibits a distinct electronic structure from other iron-based superconductors.Exploiting polarization-dependent angle-resolved photoemission spectroscopy,we have determined the orbital characters of band structure in aKxFe2ySe2superconductor.To a large extent,we find thatKxFe2ySe2superconductor shares similar orbital characters with other iron-based superconductors,but with its own characteristics.For example,we have resolved two highly degenerate electron cylinders around the zone corner in the s and p geometries,respectively,indicating negligible interactions between them.Moreover,in contrast to the band calculation results,the small electron pocket around Z is found to be mainly consisted of the d z 2 orbital.The determined orbital characters would help to construct a realistic model forKxFe2ySe2.
