  We investigate the structural and magnetic properties of
La$_{0.7}$Sr$_{0.3}$CrO$_3$ (LSCO)/La$_{0.7}$Sr$_{0.3}$MnO$_3$(LSMO)
heterostructures grown on (001)-oriented MgO by molecular beam epitaxy. Due to
the large film-substrate lattice mismatch, strain relaxation is found to occur
within the first 2-3 unit cells (uc) of the film as evidenced by reflection
high energy electron diffraction and high-resolution synchrotron X-ray
reciprocal space mapping. We find that the presence of the LSCO spacer and
capping layers leads to ferromagnetism in ultra-thin LSMO layers with
thicknesses on the order of 2 uc with the magnetic easy axis oriented in the
film plane. Net magnetic moments of 1.4 and 2.4 $\mu_B$/Mn are measured for [2
uc LSCO/ 2 uc LSMO] and [2 uc LSCO/ 4 uc LSMO] superlattices, respectively by
SQUID magnetometry. The effective magnetic anisotropy of the relaxed [2 uc
LSCO/ 4 uc LSMO] heterostructure is found to be an order of magnitude higher
than bulk LSMO highlighting the critical role of interfacial magnetic exchange
interactions in tuning magnetic anisotropy at complex oxide interfaces.
