title: Probing the electronic and spintronic properties of buried interfaces by extremely low energy photoemission spectroscopy.
abstract: Ultraviolet photoemission spectroscopy (UPS) is a powerful tool to study the electronic spin and symmetry features at both surfaces and interfaces to ultrathin top layers. However, the very low mean free path of the photoelectrons usually prevents a direct access to the properties of buried interfaces. The latter are of particular interest since they crucially influence the performance of spintronic devices like magnetic tunnel junctions (MTJs). Here, we introduce spin-resolved extremely low energy photoemission spectroscopy (ELEPS) to provide a powerful way for overcoming this limitation. We apply ELEPS to the interface formed between the half-metallic Heusler compound Co2MnSi and the insulator MgO, prepared as in state-of-the-art Co2MnSi/MgO-based MTJs. The high accordance between the spintronic fingerprint of the free Co2MnSi surface and the Co2MnSi/MgO interface buried below up to 4 nm MgO provides clear evidence for the high interface sensitivity of ELEPS to buried interfaces. Although the absolute values of the interface spin polarization are well below 100%, the now accessible spin- and symmetry-resolved wave functions are in line with the predicted existence of non-collinear spin moments at the Co2MnSi/MgO interface, one of the mechanisms evoked to explain the controversially discussed performance loss of Heusler-based MTJs at room temperature.
authors.affiliation: Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger Str. 46, 67663 Kaiserslautern, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Fetzer
authors.affiliation: Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger Str. 46, 67663 Kaiserslautern, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Stadtmüller
authors.affiliation: Department of Applied Physics, Graduate School of Engineering, Tohoku University, aoba-yama 6-6-05, Sendai 980-8579, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ohdaira
authors.affiliation: Department of Applied Physics, Graduate School of Engineering, Tohoku University, aoba-yama 6-6-05, Sendai 980-8579, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Naganuma
authors.affiliation: Department of Applied Physics, Graduate School of Engineering, Tohoku University, aoba-yama 6-6-05, Sendai 980-8579, Japan.
authors.forename: Mikihiko
authors.initials: M
authors.lastname: Oogane
authors.affiliation: Department of Applied Physics, Graduate School of Engineering, Tohoku University, aoba-yama 6-6-05, Sendai 980-8579, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ando
authors.affiliation: Division of Electronics for Informatics, Hokkaido University, Kita 14 Nishi 9, Sapporo 060-0814, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Taira
authors.affiliation: Division of Electronics for Informatics, Hokkaido University, Kita 14 Nishi 9, Sapporo 060-0814, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Uemura
authors.affiliation: Division of Electronics for Informatics, Hokkaido University, Kita 14 Nishi 9, Sapporo 060-0814, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger Str. 46, 67663 Kaiserslautern, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Aeschlimann
authors.affiliation: Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger Str. 46, 67663 Kaiserslautern, Germany.
authors.forename: Mirko
authors.initials: M
authors.lastname: Cinchetti