Upper Limit to Magnetism in LaAlO3/SrTiO3 Heterostructures

Using polarized neutron reflectometry we measured the neutron spin-dependent reflectivity from four LaAlO3/SrTiO3 superlattices. Our results imply that the upper limit for the magnetization averaged over the lateral dimensions of the sample induced by an 11 T magnetic field at 1.7 K is less than 2 G. SQUID magnetometry of the neutron superlattice samples sporadically finds an enhanced moment, possibly due to experimental artifacts. These observations set important restrictions on theories which imply a strongly enhanced magnetism at the interface between LaAlO3 and SrTiO3.