displays a TC of 182 K, greatly enhanced compared with the plain LCMO film at 2.8 nm (20)
but lower than the corresponding LCMO/CRO
SL (TC 265 K), which is fabricated for comparison. The difference in TC of the two SLs can
be ascribed to a relatively weakened electron
leakage at the LCMO/CRTO interfaces caused by
the depletion of Ru 4d band by Ti doping (19).
Notably, the LCMO/CRTO SL shows a decrease
of moments at 140 K, also in sharp contrast to the
LCMO/CRO SL. Given the negligible magnetism
in ultrathin CRTO films (fig. S1), such a drop in
magnetization is recognized as a signature of the
AF-IEC between FM LCMO layers across the
CRTO spacers. This assertion can be confirmed
by the hysteresis loops shown in the inset of
Fig. 1A. Although the LCMO/CRO SL shows an
almost square loop, the LCMO/CRTO SL shows a
negligible MR with MR/MS 3%, where MR (MS)
is the remanent (saturation) magnetization. More-
over, the loop exhibits multiple discrete steps with
two magnetization plateaus at ±1/5MS (for a
full set of loops at various temperatures, see fig.
S5), which provides concrete evidence for the
AF-IEC in the LCMO/CRTO SL.
To explain the magnetization plateaus, we
first examine the magnetic switching behavior
192 14 JULY 2017 • VOL 357 ISSUE 6347 sciencemag.org SCIENCE
Fig. 1. AF-IEC in LCMO/
(A) Temperature (T)
dependence of normalized
measured in LCMO/CRTO
and LCMO/CRO SLs,
[2.8/1.2]10. The paramagnetic background from
the NGO(001) substrates
is included for comparison.
During these measurements, a cooling field of
250 Oe is applied along
the in-plane easy-axis
. The inset shows the
loops measured at 50 K
from each SL, with the
from the NGO substrate
subtracted (figs. S3 and S4).
(B) Hysteresis loops
measured at 100 K from LCMO/CRTO SLs, [2.8/1.2]N, with N = 2, 3, and 4, respectively. For clarity, the steplike loop measured with the magnetic field
(H) sweeping from positive (negative) to negative (positive) is denoted with solid (open) circles (fig. S6). (C) Two possible magnetic configurations of the
intermediate state for the N = 4 SL, which has the magnetization plateau at 1/2MS. (D) PNR measured at 10 K from LCMO/CRTO SL, [2.8/1.2]10, with
the field of 30 Oe (top) or 5000 Oe (bottom) applied along the in-plane easy-axis .
Fig. 2. Dependence of IEC on
layer thicknesses. Normalized M-T
curves and M-H hysteresis loops
measured from the LCMO/CRTO
SLs, [x/1.2]10, with varying LCMO
thicknesses (A and B) and [3.2/y]10
with varying CRTO thicknesses
(C and D). During the measurements, the field is applied along the
in-plane easy-axis . For the
M-Tcurves, the cooling field is set at
250 Oe, and for each hysteresis
loop, the paramagnetic background
from the NGO substrate is subtracted.
(E) The exchange field Hex1 plots
against the LCMO thickness (x)
extracted from (B); the data measured
at 100 K for the N = 2 SLs are also
shown. Lines are guides to the eye.
(F) Hex1 plots against the CRTO
thickness (y) extracted from (D); the
data measured at 100 K for the
N = 2 SLs (x = 2.8 nm) are also shown.
For the samples with FM-like hysteresis
loops, Hex is set at zero. The solid
line is an exponential fitting to the data
extracted from the N = 2 SLs.