We present measurements of tunneling spin polarization of Co72Fe20B8 in Al/AlOx/CoFeB tunnel junctions using superconducting tunneling spectroscopy. We consistently observe high spin polarization (above 53%), higher than that measured for comparable CoFe alloys, indicating a crucial role played by the 8% atomic boron. X-ray diffraction measurements on 700 Å thick films reveal an amorphous structure for as-deposited films, while anneals above 250¿°C initiate a gradual crystallization. Superconducting quantum interference device magnetometery shows that the magnetic moment exhibits minor changes after anneals, but there is a dramatic change in the coercivity after anneals above 400¿°C. However, these structural and magnetic changes induce only a slight change in the tunneling spin polarization of CoFeB.
|Title of host publication||Proceedings of the annual scientific meeting FOM-Decemberdagen, 13-14 dec 2005, Veldhoven, the Netherlands|
|Publication status||Published - 2005|