The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yoshio Miura - One of the best experts on this subject based on the ideXlab platform.
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electronic and Magnetic properties of off stoichiometric co 2 mn β si mgo interfaces studied by x ray Magnetic Circular Dichroism
Journal of Applied Physics, 2015Co-Authors: V R Singh, V K Verma, K Ishigami, Goro Shibata, A Fujimori, T Koide, Yoshio MiuraAbstract:We have studied the electronic and Magnetic states of Co and Mn atoms at the interface of the Co2MnβSi (CMS)/MgO (β = 0.69, 0.99, 1.15, and 1.29) Magnetic tunnel junction (MTJ) by means of x-ray Magnetic Circular Dichroism. In particular, the Mn composition (β) dependences of the Mn and Co Magnetic moments were investigated. The experimental spin Magnetic moments of Mn, mspin(Mn), derived from x-ray Magnetic Circular Dichroism weakly decreased with increasing Mn composition β in going from Mn-deficient to Mn-rich CMS films. This behavior was explained by first-principles calculations based on the antisite-based site-specific formula unit (SSFU) composition model, which assumes the formation of only antisite defect, not vacancies, to accommodate off-stoichiometry. Furthermore, the experimental spin Magnetic moments of Co, mspin(Co), also weakly decreased with increasing Mn composition. This behavior was consistently explained by the antisite-based SSFU model, in particular, by the decrease in the concentra...
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Magnetic anisotropy in ta cofeb mgo investigated by x ray Magnetic Circular Dichroism and first principles calculation
Applied Physics Letters, 2014Co-Authors: Shun Kanai, Yoshio Miura, F Matsukura, Masahito Tsujikawa, Masafumi Shirai, Hideo OhnoAbstract:We study the spin and orbital Magnetic moments in Ta/Co0.4Fe0.4B0.2/MgO by x-ray Magnetic Circular Dichroism measurements as well as first-principles calculations, in order to clarify the origin of the perpendicular Magnetic anisotropy. Both experimental and theoretical results show that orbital Magnetic moment of Fe is more anisotropic than that of Co with respect to the magnetization direction. The anisotropy is larger for thinner CoFeB, indicating that Fe atoms at the interface with MgO contribute more than Co to the observed perpendicular Magnetic anisotropy.
F Sette - One of the best experts on this subject based on the ideXlab platform.
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experimental confirmation of the x ray Magnetic Circular Dichroism sum rules for iron and cobalt
Physical Review Letters, 1995Co-Authors: C T Chen, Y U Idzerda, N V Smith, G Meigs, E E Chaban, G H Ho, E Pellegrin, F SetteAbstract:High precision, {ital L}{sub 2,3}-edge photoabsorption and Magnetic Circular Dichroism spectra of iron and cobalt were measured in transmission with {ital in} {ital situ} grown thin films, eliminating experimental artifacts encountered by the indirect methods used in all previous measurements. The Magnetic moments determined from the integrals of these spectra are found to be in excellent agreement (within 3%) for the orbital to spin moment ratios, and in good agreement (within 7%) for the individual moments, with those obtained from Einstein--de Haas gyroMagnetic ratio measurements, demonstrating decisively the applicability of the individual orbital and spin sum rules.
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exchange spin orbit and correlation effects in the soft x ray Magnetic Circular Dichroism spectrum of nickel
Physical Review B, 1991Co-Authors: C T Chen, N V Smith, F SetteAbstract:A tight-binding analysis of soft-x-ray-absorption and Magnetic-Circular-Dichroism (MCD) spectra on Ni at the 2p\ensuremath{\rightarrow}3d thresholds yields values for the valence spin-orbit parameter and exchange splitting which are, respectively, larger and smaller than the ground-state band-structure values by a factor of \ensuremath{\sim}2. The discrepancies are attributed to core-hole correlation effects. A feature that appears 4 eV above the main white lines, but only in the MCD spectrum, is also attributed to correlation effects.
Victor N. Nemykin - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Circular Dichroism of transition metal complexes of perfluorophenyl n confused porphyrins inverting electronic structure through a proton
Journal of Physical Chemistry A, 2017Co-Authors: Samantha J Doble, Christopher J. Ziegler, Allen J Osinski, Shelby M Holland, Julia M Fisher, Richard G Geier, Rodion V Belosludov, Victor N. NemykinAbstract:Neutral and deprotonated anionic Ni(II), Pd(II), Cu(II), and Cu(III) complexes of tetrakis(perfluorophenyl)-N-confused porphyrin (PF-NCP) were prepared and investigated by UV–visible and Magnetic Circular Dichroism (MCD) spectroscopies. As in the previously reported Ni(II) adduct of tetraphenyl N-confused porphyrin, we observe sign reverse (positive to negative intensities with increasing energy) features in the MCD spectra of the neutral Ni(II), Pd(II), and Cu(II) complexes of PF-NCP, which is indicative of rare ΔHOMO ΔLUMO condition. The Cu(III) PF-NCP complex shows features similar to those of the deprotonated divalent metal systems. Spectroscopic features in all target complexes as well as previously published metal-free and Ni(II) NCP systems were correlated with the density functional theory (DFT) and time-dependent DFT (TDD...
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Magnetic Circular Dichroism spectroscopy of meso tetraphenylporphyrin derived hydroporphyrins and pyrrole modified porphyrins
Journal of Physical Chemistry A, 2016Co-Authors: Hannah M. Rhoda, Joshua Akhigbe, Christian Brückner, Junichi Ogikubo, Jared R. Sabin, Christopher J. Ziegler, Victor N. NemykinAbstract:A large set of free-base and transition-metal 5,10,15,20-tetraphenyl-substituted chlorins, bacteriochlorins, and isobacteriochlorins and their pyrrole-modified analogues were investigated by combined UV–visible spectroscopy, Magnetic Circular Dichroism (MCD), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches and their spectral characteristics were compared to those of the parent compounds, free-base tetraphenylporphyrin 1H2 and chlorin 2H2. It was shown that the nature of the pyrroline substituents in the chlorin derivatives dictates their specific UV–vis and MCD spectroscopic signatures. In all hydroporphyrin-like cases, MCD spectroscopy suggests that the ΔHOMO is smaller than the ΔLUMO for the macrocycle-centered frontier molecular orbitals. DFT and TDDFT calculations were able to explain the large broadening of the UV–vis and MCD spectra of the chlorin diones and their derivatives compared to the other hydroporphyrins and hydroporphyrin analogues. This study contributes to the ...
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Magnetic Circular Dichroism Spectroscopy of meso-Tetraphenylporphyrin-Derived Hydroporphyrins and Pyrrole-Modified Porphyrins
2016Co-Authors: Hannah M. Rhoda, Joshua Akhigbe, Junichi Ogikubo, Jared R. Sabin, Christopher J. Ziegler, Christian Brückner, Victor N. NemykinAbstract:A large set of free-base and transition-metal 5,10,15,20-tetraphenyl-substituted chlorins, bacteriochlorins, and isobacteriochlorins and their pyrrole-modified analogues were investigated by combined UV–visible spectroscopy, Magnetic Circular Dichroism (MCD), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches and their spectral characteristics were compared to those of the parent compounds, free-base tetraphenylporphyrin 1H2 and chlorin 2H2. It was shown that the nature of the pyrroline substituents in the chlorin derivatives dictates their specific UV–vis and MCD spectroscopic signatures. In all hydroporphyrin-like cases, MCD spectroscopy suggests that the ΔHOMO is smaller than the ΔLUMO for the macrocycle-centered frontier molecular orbitals. DFT and TDDFT calculations were able to explain the large broadening of the UV–vis and MCD spectra of the chlorin diones and their derivatives compared to the other hydroporphyrins and hydroporphyrin analogues. This study contributes to the further understanding of the electronic effects of replacing a pyrrole in porphyrins by pyrrolines or other five-membered heterocycles (oxazoles and imidazoles)
K Hirsch - One of the best experts on this subject based on the ideXlab platform.
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femtosecond x ray Magnetic Circular Dichroism absorption spectroscopy at an x ray free electron laser
Review of Scientific Instruments, 2016Co-Authors: Daniel J Higley, K Hirsch, Georgi L Dakovski, Emmanuelle Jal, Edwin Yuan, Tianmin Liu, Alberto Lutman, James P Macarthur, Elke Arenholz, Zhao ChenAbstract:X-ray Magnetic Circular Dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L3,2-edges. The high brightness of the X-ray free electron laser combined with high accuracy detection of incident and transmitted X-rays enables ultrafast X-ray Magnetic Circular Dichroism studies of unprecedented sensitivity. This new capability is applied to a study of all-optical Magnetic switching dynamics of Fe and Gd Magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature.
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electronic ground states of fe2 and co2 as determined by x ray absorption and x ray Magnetic Circular Dichroism spectroscopy
Journal of Chemical Physics, 2015Co-Authors: V Zamudiobayer, K Hirsch, A Langenberg, A ławicki, Akira Terasaki, Bernd Von IssendorffAbstract:The (6)Π electronic ground state of the Co2 (+) diatomic molecular cation has been assigned experimentally by x-ray absorption and x-ray Magnetic Circular Dichroism spectroscopy in a cryogenic ion trap. Three candidates, (6)Φ, (8)Φ, and (8)Γ, for the electronic ground state of Fe2 (+) have been identified. These states carry sizable orbital angular momenta that disagree with theoretical predictions from multireference configuration interaction and density functional theory. Our results show that the ground states of neutral and cationic diatomic molecules of 3d transition elements cannot generally be assumed to be connected by a one-electron process.
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femtosecond x ray Magnetic Circular Dichroism absorption spectroscopy at an x ray free electron laser
arXiv: Materials Science, 2015Co-Authors: Daniel J Higley, K Hirsch, Georgi L Dakovski, Emmanuelle Jal, Edwin Yuan, Tianmin Liu, Alberto Lutman, James P Macarthur, Elke Arenholz, Zhao ChenAbstract:X-ray Magnetic Circular Dichroism spectroscopy using an X-ray free electron laser is demonstrated with spectra over the Fe L$_{3,2}$-edges. This new ultrafast time-resolved capability is then applied to a fluence-dependent study of all-optical Magnetic switching dynamics of Fe and Gd Magnetic sublattices in a GdFeCo thin film above its magnetization compensation temperature. At the Magnetic switching fuence, we corroborate the existence of a transient ferroMagnetic-like state. The timescales of the dynamics, however, are longer than previously observed below the magnetization compensation temperature. Above and below the switching fluence range, we observe secondary demagnetization with about 5 ps timescales. This indicates that the spin thermalization takes longer than 5 ps.
Dingsheng Wang - One of the best experts on this subject based on the ideXlab platform.
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first principles investigation of the validity and range of applicability of the x ray Magnetic Circular Dichroism sum rule
Physical Review Letters, 1993Co-Authors: Dingsheng Wang, Arthur J FreemanAbstract:X-ray Magnetic Circular Dichroism (MCD) spectra and orbital angular momentum, [l angle][ital L][sub [ital z]][r angle], for transition metal bulk and surfaces were studied for both ground state and core hole excitations using a highly precise local density approach. For Fe(001), we predict a double peak structure in both the MCD and total absorption spectra and a strong enhancement of [l angle][ital I][sub [ital z]][r angle]. Surprisingly, the MCD orbital sum rule is found to be valid to within (5--10)%. Finally, the results suggest possible solutions to several problems faced in applying the MCD sum rule to measure [l angle][ital L][sub [ital z]][r angle].
