Interface-driven magnetic anisotropy in relaxed La$_{0.7}$Sr$_{0.3}$CrO$_3$/La$_{0.7}$Sr$_{0.3}$MnO$_3$ heterostructures on MgO

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.