416 research outputs found
Large spin-orbit splitting and weakly-anisotropic superconductivity revealed with single-crystalline noncentrosymmetric CaIrSi3
We report normal and superconducting properties of the Rashba-type
noncentrosymmetric com- pound CaIrSi3, using single crystalline samples with
nearly 100% superconducting volume fraction. The electronic density of states
revealed by the hard x-ray photoemission spectroscopy can be well explained by
the relativistic first-principle band calculation. This indicates that strong
spin-orbit interaction indeed affects the electronic states of this compound.
The obtained H - T phase diagram exhibits only approximately 10% anisotropy,
indicating that the superconducting properties are almost three dimensional.
Nevertheless, strongly anisotropic vortex pinning is observed.Comment: 8 pages, 6 figures, 1 table, accepted for publication in Phys. Rev.
Properties of the quaternary half-metal-type Heusler alloy CoMnFeSi
This work reports on the bulk properties of the quaternary Heusler alloy
CoMnFeSi with the Fe concentration . All samples, which
were prepared by arc melting, exhibit long range order over the complete
range of Fe concentration. Structural and magnetic properties of
CoMnFeSi Heusler alloys were investigated by means of X-ray
diffraction, high and low temperature magnetometry, M{\"o\ss}bauer
spectroscopy, and differential scanning calorimetry. The electronic structure
was explored by means of high energy photo emission spectroscopy at about 8 keV
photon energy. This ensures true bulk sensitivity of the measurements. The
magnetization of the Fe doped Heusler alloys is in agreement with the values of
the magnetic moments expected for a Slater-Pauling like behavior of
half-metallic ferromagnets. The experimental findings are discussed on the hand
of self-consistent calculations of the electronic and magnetic structure. To
achieve good agreement with experiment, the calculations indicate that on-site
electron-electron correlation must be taken into account, even at low Fe
concentration. The present investigation focuses on searching for the
quaternary compound where the half-metallic behavior is stable against outside
influences. Overall, the results suggest that the best candidate may be found
at an iron concentration of about 50%.Comment: 26 pages, 9 figures Phys. Rev. B accepte
A p-type Heusler compound: Growth, structure, and properties of epitaxial thin NiYBi films on MgO(100)
Epitaxial semiconducting NiYBi thin films were directly prepared on MgO(100)
substrates by magnetron sputtering. The intensity ratio of the (200) and (400)
diffraction peaks, I(200)/I(400) = 2.93, was close to the theoretical value
(3.03). The electronic structure of NiYBi was calculated using WIEN2k and a
narrow indirect band gap of width 210 meV was found. The valence band spectra
of the films obtained by linear dichroism in hard X-ray photoelectron
spectroscopy exhibit clear structures that are in good agreement with the
calculated band structure of NiYBi
Electronic correlations and Hund's coupling effects in SrMoO revealed by photoemission spectroscopy
We investigate the electronic structure of a perovskite-type Pauli paramagnet
SrMoO3 (t2g2) thin film using hard x-ray photoemission spectroscopy and compare
the results to the realistic calculations that combine the density functional
theory within the local-density approximation (LDA) with the dynamical-mean
field theory (DMFT). Despite the clear signature of electron correlations in
the electronic specific heat, the narrowing of the quasiparticle bands is not
observed in the photoemission spectrum. This is explained in terms of the
characteristic effect of Hund's rule coupling for partially-filled t2g bands,
which induces strong quasiparticle renormalization already for values of
Hubbard interaction which are smaller than the bandwidth. The interpretation is
supported by additional model DMFT calculations including Hund's rule coupling,
that show renormalization of low-energy quasiparticles without affecting the
overall bandwidth. The photoemission spectra show additional spectral weight
around -2 eV that is not present in the LDA+DMFT. We interpret this weight as a
plasmon satellite, which is supported by measured Mo, Sr and Oxygen core-hole
spectra that all show satellites at this energy.Comment: 8 pages, 7 figure
Recoil effects of photoelectrons in a solid
High energy resolution C 1 photoelectron spectra of graphite were measured
at the excitation energy of 340, 870, 5950 and 7940eV using synchrotron
radiation. On increasing the excitation energy, i.e., increasing kinetic energy
of the photoelectron, the bulk origin C 1 peak position shifts to higher
binding energies. This systematic shift is due to the kinetic energy loss of
the high-energy photoelectron by kicking the atom, and is clear evidence of the
recoil effect in photoelectron emission. It is also observed that the
asymmetric broadening increases for the higher energy photoelectrons. All these
recoil effects can be quantified in the same manner as the M\"ossbauer effect
for -ray emission from nuclei embedded in crystals.Comment: 4 pages, 2 figure
Investigation on MnGa/MgO interface for magnetic tunneling junctions
The MnGa Heusler compound and related alloys are the most promising
materials for the realization of spin-transfer-torque switching in magneto
tunneling junctions. Improved performance can be achieved by high quality
interfaces in these multilayered structured devices. In this context, the
interface between MnGa and MgO is of particular interest because of
its spin polarization properties in tunneling junctions. We performed a
chemical characterization of the MgO/MnGa junction by hard x-ray
photoelectron spectroscopy (HAXPES). The experiment indicated the formation of
Ga-O bonds at the interface and evidenced changes in the local environment of
Mn atoms in the proximity of the MgO film. In addition, we show that the
insertion of a metallic Mg-layer interfacing the MgO and Mn--Ga film strongly
suppresses the oxidation of gallium
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