Spin‐dependent tunneling in HfO2 tunnel junctions

We identified reactively sputtered HfO2 as a particularly good material for making thin insulating barriers for spin‐dependent tunnel junctions. This material allows one to form pinhole‐free tunnel barriers with good transmission of the spin polarization of the tunneling electrons. Magnetic tunnel junctions consisting of a thin layer of HfO2 sandwiched between transition metal electrodes (Co and Fe, for instance) exhibit changes of tunnel resistance up to 30% at low temperature as a function of applied field. This effect can be used in a variety of magnetic field sensing applications or in magnetic random access memory.