SUPPLEMENTAL SECTION
Electrostatic doping as a source for robust ferromagnetism at the
interface between antiferromagnetic cobalt oxides
Zi-An Li,1 N. Fontaíña-Troitiño,2 A. Kovács,3 S. Liébana-Viñas,1,2 M. Spasova,1
R. E. Dunin-Borkowski,3 M. Müller,4 D. Doennig,4 R. Pentcheva,1,4 M. Farle1 and
V. Salgueiriño2
1
Faculty of Physics and Center for Nanointegration (CENIDE),
University Duisburg-Essen 48047, Duisburg (Germany)
2
3
Departamento de Física Aplicada, Universidade de Vigo 36310, Vigo (Spain)
Ernst Ruska-Centre and Peter Grünberg Institute, Research Centre Jülich, 52425 Jülich,
(Germany)
4
Department of Earth and Environmental Sciences, Section Crystallography, LMU Munich,
Theresienstr. 41, 80333 Munich (Germany)
Table 1 Magnetic properties of Sample S-75nm
ZFC
Temperature
[K]
5
100
300
Ms+
[Am2/kg]
1.750
1.577
1.580
Ms[Am2/kg]
-1.759
-1.567
-1.573
Mr+
[Am2/kg]
0.313
0.346
0.261
Mr[Am2/kg]
-0.329
-0.364
-0.261
µ0Hc+
[mT]
50.5
57.0
35.7
µ0Hc[mT]
-57.7
-57.4
-35.4
5
100
300
1.796
1.603
1.565
-1.720
-1.535
-1.565
0.517
0.422
0.262
-0.339
-0.320
-0.262
50.7
49.4
35.6
-84.7
-69.0
-35.7
FC
Table2 Magnetic properties of Sample S-40nm
ZFC
Temperature
[K]
5
100
300
Ms+
[Am2/kg]
2.826
2.591
2.601
Ms[Am2/kg]
-2.829
-2.585
-2.597
Mr+
[Am2/kg]
0.451
0.421
0.327
Mr[Am2/kg]
-0.456
-0.424
-0.328
µ0Hc+
[mT]
42.4
42.9
28.7
µ0Hc[mT]
-42.7
-42.6
-28.7
5
100
300
2.849
2.622
2.580
-2.800
-2.587
-2.583
0.574
0.448
0.326
-0.443
-0.406
-0.326
40.6
40.3
28.5
-57.2
-44.9
-28.4
FC
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Figure S3:
STEM-EELS mapping of the CoO/Co3O4 interface of a single cobalt oxide octahedron.
a, STEM-EELS spectrum image (SI) acquired with 22x16 pixels, at 80 kV using a probe size
of 1 nm and magnified area near the crystal surface.
b, Background-subtracted typical EEL spectra at the O K-edge and Co L edges obtained from
the core (A) and shell (B) regions indicated in a. The peaks a, b, and c in the O- K edge
spectrum are commonly used as fingerprint for identifying the type of Co oxide. In
the shell region B a high intensity of peak a indicates a Co3O4 phase. In the core
region (A) peak “a” is much lower, that is typical for CoO.
c, Map of the ratio of the L edge intensities Co I(L3)/I(L2) determined from B. A ratio of 4.5
(red) and 2.4 (blue) is typical for Co in CoO and Co3O4. These values were adapted
from J. Appl. Phys. Vol 108, 063704 by Y. Zhao et al.
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Figure S2 | Temperature dependence of coercivity HC and exchange bias field (HEB) of a,
Sample S-75nm. b, Sample S-40nm. The applied cooling field is 2 Tesla. The HEB is related to
the presence of a ferromagnetic (FM)-antiferromagnetic (AFM) interface and vanishes above
the Néel temperature (TN = 291 K) of the AFM. The non-vanishing coercivity reveals the
presence of strong ferromagnetism.
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