Various devices are described (along with methods for making them), where the device has a tunnel barrier sandwiched between two magnetic layers (one of the magnetic layers functioning as a free layer and the other of the magnetic layers functioning as a reference layer). One magnetic layer underlies the tunnel barrier and the other magnetic layer overlies the tunnel barrier, thereby permitting spin-polarized current to pass across the magnetic layers and through the tunnel barrier. At least one of the magnetic layers includes a metal oxide sublayer (e.g., an MgO sublayer) sandwiched between magnetic material.