Suchergebnisse

We performed x-ray magnetic circular dichroism (XMCD) measurements on heterostructures comprising topological insulators (TIs) of the (Bi,Sb)2(Se,Te)3 family and the magnetic insulator EuS. XMCD measurements allow us to investigate element-selective magnetic proximity effects at the very TI/EuS interface. A systematic analysis reveals that there is neither significant induced magnetism within the TI nor an enhancement of the Eu magnetic moment at such interface. The induced magnetic moments in Bi, Sb, Te, and Se sites are lower than the estimated detection limit of the XMCD measurements of ∼10−3μB/at. ; This research was supported by the European Union's Horizon 2020 FET-PROACTIVE project TOCHA under Grant Agreement 824140. The authors acknowledge funding by the European Research Council under Grant Agreement No. 306652 SPINBOUND, by the CERCA Programme/Generalitat de Catalunya 2017 SGR 827, by MINECO (under Contracts No. MAT2016-75952-R, No. MAT2016-78293-C6-2-R, No. PID2019-111773RBI00/AEI/10.13039/501100011033, No. PID2019- 107338RB-C65, and Severo Ochoa No. SEV-2017-0706) and the European Regional Development Fund (ERDF) under the program Interreg V-A España-Francia-Andorra (Contract No. EFA 194/16 TNSI). A. I. F. acknowledges funding from MINECO-Juan de la Cierva fellowship ref. IJCI-2015-25514 and from the European Union's Horizon 2020 People Programme (Marie Skłodowska Curie Actions) H2020-MSCA-IF-2017 under REA Grant Agreement No. 796925. F. B. acknowledges funding from MINECO Ramón y Cajal Program under Contract No. RYC-2015-18523. ; Peer reviewed

We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low-and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we implement spin precession measurements under oblique magnetic fields that generate an out-of-plane spin population. We find that the spin-lifetime anisotropy of graphene on silicon oxide is independent of carrier density and temperature down to 150 K, and much weaker than previously reported. Indeed, within the experimental uncertainty, the spin relaxation is isotropic. Altogether with the gate dependence of the spin lifetime, this indicates that the spin relaxation is driven by magnetic impurities or random spin-orbit or gauge fields. ; This research was partially supported by the European Research Council under Grant Agreement No. 308023 SPINBOUND, by the Spanish Ministry of Economy and Competitiveness, MINECO (under Contract No. MAT2013-46785-P and Severo Ochoa No. SEV-2013-0295), and by the Secretariat for Universities and Research, Knowledge Department of the Generalitat de Catalunya. M.V.C., J.F.S. and J.C. acknowledge support from the Ramón y Cajal, Juan de la Cierva and Beatriu de Pinós programs, respectively. F.B. acknowledges funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013/ under REA Grant Agreement No. 624897. J.E.S. and J.V.d.V. acknowledge funding from the Methusalem Funding of the Flemish Government and the Research Foundation-Flanders (FWO). ; Peer Reviewed