the coupling is controlled by the spin-polarized
tunneling as suggested for the Fe/MgO/Fe system
(7, 33), where the coupling strength decays exponentially with increasing spacer thicknesses owing
to the evanescent electron waves (6). Hex1 of the N =
2 series at various values of y (Fig. 2F) can be well
fitted with an exponential law Hex1 º y−2exp(-y/l)
predicted by the quantum interference model (6),
with a decay length l = 0.5 nm. Therefore, such a
damping is consistent with the insulating nature
of the ultrathin CRTO spacer.
We now move to the temperature-dependent
magnetic switching and AF-IEC in this system.
A full set of hysteresis loops measured from an
optimized SL, [3.2/1.2]10, are shown in fig. S10.
For an in-plane magnetized film, the magnetic
switching is usually controlled by the competition between AF-IEC and MA (35). In the inset of
Fig. 3A, the loops measured with the magnetic
field applied along the two orthogonal in-plane
axes signify a typical uniaxial MA, with the easy-axis along  and the hard-axis along 
(fig. S7) (27). At 160 K, the anisotropy field HMA ~
950 Oe, deduced from the saturation field in
the  direction, is much larger than the exchange field of the interior LCMO layers (Hex2 =
150 Oe). This means the magnetic reversal of each
LCMO layer tends to adopt a spin-flip mode, as
manifested by the sharp steplike switching (11).
On the basis of all the loops (Fig. 3A and fig. S10),
So far, we have demonstrated AF-IEC with
layer-resolved magnetic switching for LCMO/
CRTO SLs. The results are highly reproducible,
and moreover we find that the AF-IEC is tunable
via the Ti-doping level of the CRTO spacer and
the growth orientations (fig. S13). The multiple
control of TC, MA, interfacial octahedral con-
nectivity, IEC, spin-dependent transport, and
possibly the dimensionality effect (15, 16) makes
this epitaxial system rather intriguing, encourag-
ing more detailed spectroscopic and theoretical
studies on the spacers and interfaces, including
the interfacial magnetism (37–40). We also show
how our system can be extended for possible ap-
plications. First, we modify the N = 4 SL struc-
ture by increasing the layer thickness of only the
central CRTO from y = 1.2 to 3.6 (denoted as S1).
As shown in Fig. 4A, in contrast to the N = 4 SL,
this structure maintains the remanent AF state,
but the magnetization plateaus at ±1/2MS dis-
appear. This indicates that a thicker central CRTO
layer can magnetically decouple the top and bot-
tom N = 2 S-AFMs very effectively. Similarly, a
further stack of the N = 2 SLs can progressively
enhance the MS at a moderate field but keep the
stray field negligible, properties that are deemed
highly desirable for biotechnology applications
(41). Second, we fabricate the S-AFMs with SLs (S2)
composed of CRTO and La2/3Sr1/3MnO3 (LSMO)
layers, another prototype manganite having a
TC (bulk) of 370 K. As shown in Fig. 4B, aside
from a TC of 286 K, a drop in magnetization at
227 K and the separated hysteresis loops with
magnetization plateaus at ±1/4MS (N = 8, inset)
all signify the existence of AF-IEC in this SL,
further underlining that the present S-AFMs are
attractive for spintronic applications.
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National Natural Science Foundation of China (grants 11474263,
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Materials and Methods
Figs. S1 to S13
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22 September 2016; accepted 7 June 2017
194 14 JULY 2017 • VOL 357 ISSUE 6347 sciencemag.org SCIENCE
Fig. 4. Variations on the AF-IEC system
based on the CRTO spacer. (A) M-H loops
measured at 100 K from the N = 4 SL [2.8/1.2]4
and the modified structure S1. The latter can
be regarded as two N = 2 SLs connected by a
thick CRTO spacer. (B) Normalized M-T curve
measured from the LSMO/CRTO SL (S2), [3.2/
1.2]8, with a cooling field of 300 Oe applied
along the in-plane  axis. The inset shows
the loops measured at 225 and 250 K (as
denoted in the M-T curve), respectively, with the
paramagnetic background from the NGO substrate subtracted.