Magnetometry
Magnetic hysteresis loops were performed in a SQUID and VSM at different temperatures. In all the
cases the estimated magnetic moments corresponds to the expected in the used materials. A example
of this curves is depicted in Fig S1. It is clearly seen that there is two different coercive fields. We can
compare the obtained coercive fields in these measurements with those obtained in the TMR
measurements (Fig. 1a in the main paper). We observed a diminished coercive field in the patterned
layers, in our opinion the reduced coercivity corresponds to effect of a geometrical enhancement of the
demagnetization field that diminishes the coercive field.
Transmission electron microscopy
The studied tunnel junctions were studied using a spherical aberration (Cs)-corrected Scanning
Transmission Electron Microscope equipped with a High Angle Annular Dark Field detector (STEMHAADF technique), with a working voltage of 300KV and a camera length of 77mm. By means of
aberration correction of the condenser lens system a very small probe (sub-Ångstrom) is formed. As
the probe scans the sample the image is formed point by point, with a spatial resolution of 0.8Å.
The contrast of a STEM-HAADF image depends on the thickness of the sample and the atomic
number of the elements in the material, being approximately proportional to Z2. Moreover, aberration
correction of the probe allows the resolution of each atomic column. Therefore, for a uniformly thin
sample this technique is very useful to distinguish the different layers in the stack at the atomic scale.
Figure S2 shows a continuous barrier that assures that all the conduction is given by tunneling. No
atomic diffusion or segregation is observed between the layers, and there are hardly one or two atomic
row steps at the interface. Moreover, no extended atomic defects or dislocations were observed at the
interface by direct observation.
The samples were prepared by focused-ion-beam milling (FIB) in a JMDT-Helios 650 and measured
in a Cs-probe corrected Titan microscope (FEI). Both sample preparation and STEM analysis were
performed at the Advanced Microscopy Laboratory (LMA-INA) in Zaragoza.
Figure Captions
Figure 1S : Magnetic hysteresis loop taken at 5K and the magnetic field applied along the easy axis. Two coercive
fields are clearly identified; the first corresponds to the soft layer and second to the LSMRO/LSMO layer (see main
text for thickness).
Figure 2S (color online): STEM HAADF image of the tunnel junction. The estimated thickness of the tunnel barrier is
about 3nm and we can observe that the barrier is continuous along all the structure.