scholarly journals Механизм открытия щели в точке Дирака в электронном спектре Gd-допированного топологического изолятора

2020 ◽  
Vol 62 (2) ◽  
pp. 286
Author(s):  
А.М. Шикин ◽  
Д.А. Естюнин ◽  
А.В. Королева ◽  
Д.А. Глазкова ◽  
Т.П. Макарова ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Long Range ◽  
Photoelectron Spectroscopy ◽  
Dirac Point ◽  
Energy Gap ◽  
Magnetic Transition ◽  
Magnetic Ordering ◽  
Photoelectron Spectra ◽  
Dirac Cone ◽  
Antiferromagnetic Ordering

The electronic structure of magnetically-doped TI with stoichiometry Bi1.09Gd0.06Sb0.85Te3 in the region of the Dirac point has been studied in detail by angle-resolved photoelectron spectroscopy (ARPES) at various temperatures (above and below the Néel temperature, 1-35 K) and different polarizations of synchrotron radiation. It has shown that the energy gap in photoemission spectra opens at the Dirac point and remains open above the temperature of the long-range magnetic ordering, Tn. Measurements of magnetic properties by the superconducting magnetometry method (SQUID) have shown antiferromagnetic ordering with a transition temperature to the paramagnetic phase equal to 8.3 K. Study of the temperature dependence of the Dirac cone state intensity at the Г point by ARPES has confirmed the magnetic transition and has shown a possibility of its indication directly from photoemission spectra. A more detailed analysis of the splitting between the upper and lower Dirac cone states (i.e. the energy gap) at the Dirac point in the photoelectron spectra has shown the dependence of the measured gap on the synchrotron radiation polarization (about 28-30 meV for p-polarization and 22-25 meV for circularly polarized radiation of opposite chirality). The mechanism of opening the gap at a Dirac point above the Tn was proposed due to the “pairing” of the Dirac fermions with opposite momentum and spin orientation as a result of their interaction with the spin texture generated by photoemission in the region of the photoemission hole on a magnetic impurity atom (Gd). It was shown that the gap at the Dirac point, measured above Tn, is dynamic and is formed directly during photoemission process. At the same time, the origin of the gap remains magnetic (even when the long-range magnetic ordering is destroyed) and is associated with the properties of the magnetic topological insulator that determines a practically unchanged size of the gap above Tn. The dynamic origin of the generated gap is confirmed by the dependence of its magnitude on the polarization of synchrotron radiation.

The study of the electronic structure of some N-heterocyclic carbenes (NHCs) by variable energy photoelectron spectroscopy

2015 ◽  
Vol 17 (16) ◽  
pp. 10656-10667 ◽  
Author(s):  
Branka Kovač ◽  
Ivan Ljubić ◽  
Antti Kivimäki ◽  
Marcello Coreno ◽  
Igor Novak
Keyword(s):  
Electronic Structure ◽  
Synchrotron Radiation ◽  
Computational Methods ◽  
Photoelectron Spectroscopy ◽  
Electronic Structures ◽  
Heterocyclic Carbenes ◽  
Photoelectron Spectra ◽  
X Ray ◽  
Variable Energy

UV and X-ray photoelectron spectra of three N-heterocyclic carbenes under synchrotron radiation reveal details of their electronic structure and are used as a benchmark to test computational methods for treating core ionizations in systems with unusual electronic structures.

Real-time analysis for MBE by time-resolved core-level photoelectron spectroscopy

1998 ◽  
Vol 5 (3) ◽  
pp. 1026-1028 ◽  
Author(s):  
Fumihiko Maeda ◽  
Yoshio Watanabe ◽  
Masaharu Oshima ◽  
Masami Taguchi ◽  
Retsu Oiwa
Keyword(s):  
Synchrotron Radiation ◽  
Real Time ◽  
Photoelectron Spectroscopy ◽  
Measurement Method ◽  
Photoelectron Spectra ◽  
Time Analysis ◽  
Time Resolved ◽  
Molecular Beam Epitaxial ◽  
Real Time Analysis ◽  
Molecular Beam Epitaxial Growth

A system has been developed for the real-time analysis of surface reactions during molecular beam epitaxial growth which uses photoelectron spectroscopy with VUV light taken from synchrotron radiation. This system consists of a synchrotron radiation beamline and growth/analysis apparatus in which photoelectron spectroscopy is performed with sub-second time resolution. In this system, photoelectron spectra are measured in sequence by a `non-scanning' measurement method that enables the acquisition of snapshot photoelectron spectra using a multi-channel detector. This non-scanning measurement method was enabled by equipping an electric field correction grid. This system was used to monitor the photoelectron spectra of a GaSb(001) surface.

scholarly journals Coexistence of Spin Canting and Metamagnetism in a One-Dimensional Mn(II) Compound Bridged by Alternating Double End-to-End and Double End-On Azido Ligands and the Analog Co(II) Compound

2021 ◽  
Vol 7 (4) ◽  
pp. 50
Author(s):  
Nesrine Benamara ◽  
Zouaoui Setifi ◽  
Chen-I Yang ◽  
Sylvain Bernès ◽  
David K. Geiger ◽  
...  
Keyword(s):  
Magnetic Transition ◽  
Magnetic Ordering ◽  
Weak Ferromagnetism ◽  
Molecular Structures ◽  
Spin Canting ◽  
Manganese Compound ◽  
Space Groups ◽  
Antiferromagnetic Ordering ◽  
End To End ◽  
Interchain Interactions

Two new compounds of general formula [M(N3)2(dmbpy)] in which dmbpy = 5,5′-dimethyl-2,2′-bipyridine, and M = Mn(II) or Co(II), have been solvothermally synthesized and characterized structurally and magnetically. The structures consist of zig-zag polymeric chains with alternating bis-µ(azide-N1)2M and bis-µ(azide-N1,N3)2M units in which the cis-octahedrally based coordination geometry is completed by the N,N’-chelating ligand dmbpy. The molecular structures are basically the same for each metal. The Mn(II) compound has a slightly different packing mode compared to the Co(II) compound, resulting from their different space groups. Interestingly, relatively weak interchain interactions are present in both compounds and this originates from π–π stacking between the dmbpy rings. The magnetic properties of both compounds have been investigated down to 2 K. The measurements indicate that the manganese compound shows spin-canted antiferromagnetic ordering with a Néel temperature of TN = 3.4 K and further, a field-induced magnetic transition of metamagnetism at temperatures below the TN. This finding affords the first example of an 1D Mn(II) compound with alternating double end-on (EO) and double end-to-end (EE) azido-bridged ligands, showing the coexistence of spin canting and metamagnetism. The cobalt compound shows a weak ferromagnetism resulting from a spin-canted antiferromagnetism and long-range magnetic ordering with a critical temperature, TC = 16.2 K.

Modulation of atomic positions in CaCu x Mn7−x O12 (x ≤ 0.1)

2009 ◽  
Vol 65 (5) ◽  
pp. 535-542 ◽  
Author(s):  
W. Sławiński ◽  
R. Przeniosło ◽  
I. Sosnowska ◽  
M. Bieringer ◽  
I. Margiolaki ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Low Temperature ◽  
Long Range ◽  
Powder Diffraction ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Neutron Powder Diffraction

The modulation of atomic positions in CaCu x Mn7−x O12 (x = 0 and 0.1) was studied using synchrotron radiation powder diffraction below 250 and 220 K, respectively. The copper-rich member CaCu x Mn7−x O12 (x = 0.23) does not show any modulation of the atomic positions at temperatures as low as 10 K. Using low-temperature neutron powder diffraction the modulation of the magnetic moments of Mn ions in CaCu x Mn7−x O12 (x = 0, 0.1 and 0.23) has been investigated. Long-range modulated magnetic ordering in CaCu x Mn7−x O12 (x = 0, 0.1 and 0.23) is observed below 90.4, 89.2 and 78.1 K. (0,0,q p) and (0,0,q m) are the propagation vectors describing the modulations of the atomic positions and the magnetic moments. For CaCu x Mn7−x O12 (x = 0 and 0.1) the magnetic modulation and atomic modulation lengths are related by a factor of 2 satisfying the relation (1 − q p) = 2(1 − q m).

scholarly journals Photoelectron spectroscopy of boron-containing reactive intermediates using synchrotron radiation: BH2, BH, and BF

2020 ◽  
Vol 22 (3) ◽  
pp. 1027-1034
Author(s):  
D. P. Mukhopadhyay ◽  
D. Schleier ◽  
I. Fischer ◽  
J.-C. Loison ◽  
C. Alcaraz ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Photoelectron Spectroscopy ◽  
Reactive Intermediates ◽  
Reactive Species ◽  
Photoelectron Spectra ◽  
Coincidence Spectroscopy

Mass selected slow photoelectron spectra (SPES) of three boron-containing reactive species, BH2, BH, and BF were recorded by double imaging photoion–photoelectron coincidence spectroscopy (i2PEPICO) using synchrotron radiation.

scholarly journals Revisiting Goodenough-Kanamori rules in a new series of double perovskites LaSr1−xCaxNiReO6

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Somnath Jana ◽  
Payel Aich ◽  
P. Anil Kumar ◽  
O. K. Forslund ◽  
E. Nocerino ◽  
...  
Keyword(s):  
Long Range ◽  
Magnetic Transition ◽  
Magnetic Ordering ◽  
Double Perovskites ◽  
Ca Doping ◽  
Neutron Powder Diffraction Data ◽  
Magnetic States ◽  
Ferrimagnetic Ordering ◽  
Ordered State ◽  
Magnetic Sublattices

AbstractThe magnetic ground states in highly ordered double perovskites LaSr1−xCaxNiReO6 (x = 0.0, 0.5, 1.0) are studied in view of the Goodenough-Kanamori rules of superexchange interactions in this paper. In LaSrNiReO6, Ni and Re sublattices are found to exhibit curious magnetic states separately, but no long range magnetic ordering is achieved. The magnetic transition at ~255 K is identified with the independent Re sublattice magnetic ordering. Interestingly, the sublattice interactions are tuned by modifying the Ni-O-Re bond angles through Ca doping. Upon Ca doping, the Ni and Re sublattices start to display a ferrimagnetically ordered state at low temperature. The neutron powder diffraction data reveals long range ferrimagnetic ordering of the Ni and Re magnetic sublattices along the crystallographic b-axis. The transition temperature of the ferrimagnetic phase increases monotonically with increasing Ca concentration.

Variable-energy photoelectron spectroscopy of CpM(CO)3 (M = Mn, Re) and CpFe(CO)2I

1996 ◽  
Vol 74 (11) ◽  
pp. 2240-2249 ◽  
Author(s):  
Yong-Feng Hu ◽  
G. Michael Bancroft ◽  
Kim H. Tan ◽  
John S. Tse ◽  
Dong-Sheng Yang
Keyword(s):  
Synchrotron Radiation ◽  
Transition Metal Complexes ◽  
Photoelectron Spectroscopy ◽  
General Trend ◽  
Resonance Effect ◽  
Photoelectron Spectra ◽  
Ligand Field ◽  
Band Spectra ◽  
Variable Energy ◽  
Good Agreement

Photoelectron spectra of the valence, inner-valence, and core levels of CpM(CO)3 (M = Mn, Re) and CpFe(CO)2I were obtained using He I radiation and synchrotron radiation between 21 eV and 150 eV photon energies. The high-resolution Mn 3p, Fe 3p, and I 4d core level spectra are reported. Broadening of the I 4d spectrum is due to vibrational and ligand field splittings. Observation of the 3p spectra is critical to fully interpreting the np → nd resonance effect in the valence band spectra. This resonance effect is very useful for assigning the metal d orbital bands in the valence spectra. A Xα-SW calculation of CpMn(CO)3 was used to confirm the assignment of the valence and inner-valence orbitals. The experimental and theoretical branching ratios are in good agreement. The general trend of the metal d orbital ionization potentials for CpML3 (M = transition metal) complexes is also discussed. Key words: photoelectron, synchrotron radiation, CpMn(CO)3, CpRe(CO)3, CpFe(CO)2I, np → nd resonance, Xα-SW calculation.

scholarly journals Modification of Wood with Monoethanolamino-borate by The Data of X-Ray Photoelectron Spectroscopy

2018 ◽  
Vol 196 ◽  
pp. 04005
Author(s):  
Irina Stepina ◽  
Irina Kotlyarova
Keyword(s):  
Particle Size ◽  
Photoelectron Spectroscopy ◽  
Model Compound ◽  
Hydrolytic Stability ◽  
Photoelectron Spectra ◽  
Wood Cellulose ◽  
Rapid Loss ◽  
X Ray ◽  
Wood Protection ◽  
Cellulose Materials

The difficulty of wood protection from biocorrosion and fire is due to the fact that modifiers in use are washed out from the surface of the substrate under the influence of environmental factors. This results in a rapid loss of the protective effect and other practically important wood characteristics caused by the modification. To solve this problem is the aim of our work. Here, monoethanolaminoborate is used as a modifier, where electron-donating nitrogen atom provides a coordination number equal to four to a boron atom, which determines the hydrolytic stability of the compounds formed. Alpha-cellulose ground mechanically to a particle size of 1 mm at most was used as a model compound for the modification. X-ray photoelectron spectra were recorded on the XSAM-800 spectrometer (Kratos, UK). Prolonged extraction of the modified samples preceded the registration of the photoelectron spectra to exclude the fixation of the modifier molecules unreacted with cellulose. As a result of the experiment, boron and nitrogen atoms were found in the modified substrate, which indicated the hydrolytic stability of the bonds formed between the modifier molecules and the substrate. Therefore monoethanolaminoborate can be considered as a non-extractable modifier for wood-cellulose materials.

scholarly journals Interdependent scaling of long-range oxygen and magnetic ordering in nonstoichiometric Nd2NiO4.10

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Sumit Ranjan Maity ◽  
Monica Ceretti ◽  
Lukas Keller ◽  
Jürg Schefer ◽  
Martin Meven ◽  
...  
Keyword(s):  
Long Range ◽  
Magnetic Ordering
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