Surface State of Sacrificial Copper Electrode by Electropolishing in Hydrophobic Ionic Liquid 1‑Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Anodic dissolution of natural surface-oxidized, air-annealed, cathodically reduced, and cathodically deposited copper in hydrophobic ionic liquid 1-buthyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide under galvanostatic conditions by means of gravimetric measurements was studied. The resulting samples were mirror-like oxide-free copper pattern. The mechanism of the electropolishing of oxidized copper surface was considered. The consequent anodic reactions Cu₂O – 1e = Cu⁺ + CuO, CuO – 2e = Cu²⁺ + O, and Cu – 1e = Cu⁺ take place. The electropolishing itself occurs over oxygen-free copper surface due to competitive residual water discharge in the pits and copper dissolution on the roughness

Signatures of in-plane and out-of-plane magnetization generated by synchrotron radiation in magnetically doped and pristine topological insulators

Possibility of in-plane and out-of-plane magnetization generated by synchrotron radiation (SR) in magnetically doped and pristine topological insulators (TIs) is demonstrated and studied by angle-resolved photoemission spectroscopy. We show experimentally and by ab initio calculations how nonequal depopulation of the Dirac cone (DC) states with opposite momenta in V-doped and pristine TIs generated by linearly polarized SR leads to the hole-generated uncompensated spin accumulation followed by the SR-induced magnetization via spin-torque effect. Moreover, the photoexcitation of the DC is asymmetric, and it varies with the photon energy. We find a relation between the photoexcitation asymmetry, the generated spin accumulation, and the induced in-plane and out-of-plane magnetic field. Experimentally the SR-generated in-plane and out-of-plane magnetization is confirmed by the k∥ shift of the DC position and by the gap opening at the Dirac point even above the Curie temperature. Theoretical predictions and estimations of the measurable physical quantities substantiate the experimental results.The authors acknowledge support by Saint Petersburg State University (Grant No. 15.61.202.2015), Russian Science Foundation Grant No. 17-12-01333 (in the part of theoretical study of magnetic properties), Russian Science Foundation Grant No. 18-12-00062 (in the part of ARPES measurements and analysis of the electronic structure modification under influence of SR), and Russian Science Foundation Grant No. 17-12-01047 (in part of crystal growth and the sample characterization). The work was also supported by the Spanish Ministry of Economy and Competitiveness MINECO (Project No. FIS2016-76617-P), German-Russian Interdisciplinary Science Center (G-RISC) funded by the German Federal Foreign Office via the German Academic Exchange Service (DAAD), and Russian-German laboratory atBESSYII (Helmholtz-Zentrum Berlin).Peer reviewe