Measurement of the complex polar magneto-optical Kerr effect using weak measurement

Polar magneto-optical Kerr effect (PMOKE) is one of the most widely being applied magneto-optical Kerr effects (MOKE) due to the induced complex MOKE signal, consisting of the Kerr rotation angle and the ellipticity, is very sensitive to the magnetization component perpendicular to the magnetic surface. However, the Kerr rotation angle and the ellipticity invariably coexist and pose a challenge in their separation. This dual presence plays a pivotal role in defining the light intensity detected, ultimately restricting the advancements in the measurement precision. In this paper, we propose a weak measurement (WM) scheme to measure the complex MOKE in the pure polar configuration. Unlike the traditional MOKE or WM method using a quarter-wave-plate to measure the Kerr rotation angle and the ellipticity separately, we realize the simultaneous measurement of these two parameters in a single WM process using two new pointers, which possesses a larger linear response region compared with the previous amplified shift pointer. The measurement precision for the complex PMOKE angle reaches to $10^{-4}$ deg in our experiment. Besides, the complex magneto-optical constant Q is also calculated. This work is of great significance for the measurement of the complex PMOKE with high efficiency, ultra-precision, low cost, and is an important attempt to obtain complex physical quantities using WM

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Bulk properties of transition metals: a challenge for the design of universal density functionals

Systematic evaluation of the accuracy of exchangecorrelation functionals is essential to guide scientists in their choice of an optimal method for a given problem when using density functional theory. In this work, accuracy of one Generalized Gradient Approximation (GGA) functional, three meta-GGA functionals, one Nonseparable Gradient Approximation (NGA) functional, one meta-NGA, and three hybrid GGA functionals was evaluated for calculations of the closest interatomic distances, cohesive energies, and bulk moduli of all 3d, 4d, and 5d bulk transition metals that have face centered cubic (fcc), hexagonal closed packed (hcp), or body centered cubic (bcc) structures (a total of 27 cases). Our results show that including the extra elements of kinetic energy density and Hartree−Fock exchange energy density into gradient approximation density functionals does not usually improve them. Nevertheless, the accuracies of the Tao−Perdew−Staroverov−Scuseria (TPSS) and M06-L meta-GGAs and the MN12-L meta-NGA approach the accuracy of the Perdew−Burke−Ernzerhof (PBE) GGA, so usage of these functionals may be advisable for systems containing both solid-state transition metals and molecular species. The N12 NGA functional is also shown to be almost as accurate as PBE for bulk transition metals, and thus it could be a good choice for studies of catalysis given its proven good performance for molecular species

Critical Role of Phosphorus in Hollow Structures Cobalt-Based Phosphides as Bifunctional Catalysts for Water Splitting

Cobalt phosphides electrocatalysts have great potential for water splitting, but the unclear active sides hinder the further development of cobalt phosphides. Wherein, three different cobalt phosphides with the same hollow structure morphology (CoP-HS, CoP-HS, CoP-HS) based on the same sacrificial template of ZIF-67 are prepared. Surprisingly, these cobalt phosphides exhibit similar OER performances but quite different HER performances. The identical OER performance of these CoP-HS in alkaline solution is attributed to the similar surface reconstruction to CoOOH. CoP-HS exhibits the best catalytic activity for HER among these CoP-HS in both acidic and alkaline media, originating from the adjusted electronic density of phosphorus to affect absorption–desorption process on H. Moreover, the calculated ΔG based on P-sites of CoP-HS follows a quite similar trend with the normalized overpotential and Tafel slope, indicating the important role of P-sites for the HER process. Moreover, CoP-HS displays good performance (cell voltage of 1.67 V at a current density of 50 mA cm) and high stability in 1 M KOH. For the first time, this work detailly presents the critical role of phosphorus in cobalt-based phosphides for water splitting, which provides the guidance for future investigations on transition metal phosphides from material design to mechanism understanding.W.Z. and N.H. contributed equally to this work. X.Z. and J.F. are grateful for the Research Foundation-Flanders (FWO) project (12ZV320N). Funding from National Natural Science Foundation of China (project No.: 22005250, 21776120, and 51901161) is appreciated. M.X. is grateful to the National Natural Science Foundation of China (project No.: 22179109). W.Z. is grateful to the China Scholarship Council (NO. 201808310068). W.G. is grateful to the China Scholarship Council (NO. 201806030189). S.X. is grateful to the China Scholarship Council. K.W. is grateful to the Oversea Study Program of Guangzhou Elite Project. Funding from the Research Foundation–Flanders (FWO) (project No.: G0B3218N) and Natural Science Foundation of Fujian Province, China (No.: 2018J01433) is acknowledged. ICN2 acknowledges funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO project ECOCAT and subproject NANOGEN. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. This work has received funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No. 654360 NFFA-Europe. X.H. thanks China Scholarship Council for scholarship support (201804910551)