Title: Cation- and lattice-site-selective magnetic depth profiles of ultrathin Fe₃O₄ (001) films

Abstract

A detailed understanding of ultrathin film surface properties is crucial for the proper interpretation of spectroscopic, catalytic, and spin-transport data. We present x-ray magnetic circular dichroism (XMCD) and x-ray resonant magnetic reflectivity (XRMR) measurements on ultrathin Fe₃O₄ films to obtain magnetic depth profiles for the three resonant energies corresponding to the different cation species $\mathrm{F}{\mathrm{e}}_{\mathrm{o}\mathrm{c}\mathrm{t}}^{2+}$, $\mathrm{F}{\mathrm{e}}_{\mathrm{t}\mathrm{e}\mathrm{t}}^{3+}$, and $\mathrm{F}{\mathrm{e}}_{\mathrm{o}\mathrm{c}\mathrm{t}}^{3+}$ located on octahedral and tetrahedral sites of the inverse spinel structure of Fe₃O₄. By analyzing the XMCD spectrum of Fe₃O₄ using multiplet calculations, the resonance energy of each cation species can be isolated. Performing XRMR on these three resonant energies yields magnetic depth profiles that each correspond to one specific cation species. The depth profiles of both kinds of Fe³⁺ cations reveal a (3.9 ± 1.0) -Å -thick surface layer of enhanced magnetization, which is likely due to an excess of these ions at the expense of the $\mathrm{F}{\mathrm{e}}_{\mathrm{o}\mathrm{c}\mathrm{t}}^{2+}$ species in the surface region. The magnetically enhanced $\mathrm{F}{\mathrm{e}}_{\mathrm{t}\mathrm{e}\mathrm{t}}^{3+}$ layer is additionally shifted about 2.9 ± 0.4 Å farther from the surface than the $\mathrm{F}{\mathrm{e}}_{\mathrm{o}\mathrm{c}\mathrm{t}}^{3+}$ layer.

Authors:

Pohlmann, Tobias  ^[1];

• Search DOE PAGES for author "Pohlmann, Tobias"
• Search DOE PAGES for ORCID "0000-0002-8688-2598"

Kuschel, Timo  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-9371-8876"

Rodewald, Jari ^[3]; Thien, Jannis ^[3]; Ruwisch, Kevin ^[3]; Bertram, Florian ^[4]; Weschke, Eugen ^[5]; Shafer, Padraic ^[6]; Wollschläger, Joachim  ^[3];

• Search DOE PAGES for author "Wollschläger, Joachim"
• Search DOE PAGES for ORCID "0000-0002-3043-3718"

Küpper, Karsten  ^[3]

• Search DOE PAGES for author "Küpper, Karsten"
• Search DOE PAGES for ORCID "0000-0003-0364-9385"

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+ Show Author Affiliations

1. Osnabrück University, Osnabrück (Germany); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science
2. Bielefeld University, Bielefeld (Germany). Center for Spinelectronic Materials and Devices
3. Osnabrück University, Osnabrück (Germany)
4. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science
5. Helmholtz-Zentrum Berlin (HZB), (Germany)
6. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)

Publication Date:

Thu Dec 24 00:00:00 EST 2020

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC); Bundesministerium für Bildung und Forschung; German Research Foundation (DFG)

OSTI Identifier:

1823047

Grant/Contract Number:  

AC02-05CH11231; KU2321/6-1; WO533/20-1

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review B

Additional Journal Information:

Journal Volume: 102; Journal Issue: 22; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY