Emergent Spin-Filter at the interface between Ferromagnetic and Insulating Layered Oxides

We report a strong effect of interface-induced magnetization on the transport properties of magnetic tunnel junctions consisting of ferromagnetic manganite La${}_{0.7}$Ca${}_{0.3}$MnO${}_3$ and insulating cuprate PrBa${}_2$Cu${}_3$O${}_7$. Contrary to the typically observed steady increase of the tunnel magnetoresistance with decreasing temperature, this system exhibits a sudden anomalous decrease at low temperatures. Interestingly, this anomalous behavior can be attributed to the competition between the positive spin polarization of the manganite contacts and the negative spin-filter effect from the interface-induced Cu magnetization.