9 research outputs found
Electronic superlattice revealed by resonant scattering from random impurities in Sr3Ru2O7
Resonant elastic x-ray scattering (REXS) is an exquisite element-sensitive
tool for the study of subtle charge, orbital, and spin superlattice orders
driven by the valence electrons, which therefore escape detection in
conventional x-ray diffraction (XRD). Although the power of REXS has been
demonstrated by numerous studies of complex oxides performed in the soft x-ray
regime, the cross section and photon wavelength of the material-specific
elemental absorption edges ultimately set the limit to the smallest
superlattice amplitude and periodicity one can probe. Here we show -- with
simulations and REXS on Mn-substituted SrRuO -- that these
limitations can be overcome by performing resonant scattering experiments at
the absorption edge of a suitably-chosen, dilute impurity. This establishes
that -- in analogy with impurity-based methods used in electron-spin-resonance,
nuclear-magnetic resonance, and M\"ossbauer spectroscopy -- randomly
distributed impurities can serve as a non-invasive, but now momentum-dependent
probe, greatly extending the applicability of resonant x-ray scattering
techniques
Electronic structure of the SrTiO3 LaAlO3 interface revealed by resonant soft x ray scattering
Polarization dependent hard X-ray photoemission experiments for solids: Efficiency and limits for unraveling the orbital character of the valence band
We have investigated the efficiency and limits of polarization dependent hard X-ray photoelectron spectroscopy (HAXPES) in order to establish how well this method can be used to unravel quantitatively the contributions of the orbitals forming the valence band of solids. By rotating the energy analyzer rather than the polarization vector of the light using a phase retarder, we obtained the advantage that the full polarization of the light is available for the investigation. Using NiO, ZnO, and Cu2O as examples for solid state materials, we established that the polarization dependence is much larger than in photoemission experiments utilizing ultra-violet or soft X-ray light. Yet we also have discovered that the polarization dependence is less than complete on the basis of atomic calculations, strongly suggesting that the trajectories of the outgoing electrons are affected by appreciable side-scattering processes even at these high kinetic energies. We have found in our experiment that these can be effectively described as a directional spread of +/- 18 degrees of the photoelectrons. This knowledge allows us to identify, for example, reliably the Ni 3d spectral weight of the NiO valence band and at the same time to demonstrate the importance of the Ni 4s for the chemical stability of the compound. (C) 2014 Elsevier B.V. All rights reserved
Stoner vs. spin-mixing behavior in the bulk magnetism of Gd: A spin-resolved photoemission study
Strong ferromagnetism at the surface of an antiferromagnet caused by buried magnetic moments
Carrying a large, pure spin magnetic moment of 7 bohr/atom in the
half-filled 4f shell, divalent europium is an outstanding element for
assembling novel magnetic devices in which a two-dimensional electron gas
(2DEG) is polarized due to exchange interaction with an underlying
magnetically-active Eu layer, even in the absence of a magnetic field. A
natural example for such geometry is the intermetallic layered material
EuRhSi, in which magnetically active layers of Eu are well separated
from each other by non-magnetic Si-Rh-Si trilayers. Applying angle-resolved
photoelectron spectroscopy (ARPES) to this system, we discovered a large spin
splitting of a Shockley-type surface state formed by itinerant electrons of the
Si-Rh-Si surface related trilayer. ARPES shows that the splitting sets in below
approx. 32.5K and quickly saturates to around 150meV upon cooling.
Interestingly, this temperature is substantially higher than the order
temperature of the Eu 4f moments (approx. 24.5K) in the bulk. Our results
clearly show that the magnetic exchange interaction between the surface state
and the buried 4f moments in the 4th subsurface layer is the driving force for
the formation of itinerant ferromagnetism at the surface. We demonstrate that
the observed spin splitting of the surface state, reflecting properties of
2DEG, is easily controlled by temperature. Such a splitting may also be induced
into states of functional surface layers deposited onto the surface of
EuRhSi or similarly ordered magnetic materials with metallic or
semiconducting properties.Comment: 5 pages, 3 figure