Correlation between magnetism and spin-dependent transport in CoFeB alloys

We report a correlation between the spin polarization of the tunneling electrons (TSP) and the magnetic moment of amorphous CoFeB alloys. Such a correlation is surprising since the TSP involves s-like electrons close to the Fermi level (EF), while the magnetic moment mainly arises due to all d-electrons below EF. We show that probing the s and d-bands individually provides clear and crucial evidence for such a correlation to exist through s-d hybridization, and demonstrate the tuneability of the electronic and magnetic properties of CoFeB alloys.Comment: Accepted for publication in Physical Review Letters. Letter (4 pages) and Supplementary material (4 pages

CONTROLLING IP SPOOFING THROUGH INTER DOMAIN PACKET FILTERS

IP Spoofing is a serious threat to the legitimate use of the Internet. By employing IP spoofing, attackers can overload the destination network thus preventing it from providing service to legitimate user. In this paper, we propose an inter domain packet filter (IDPF) architecture that can minimize the level of IP spoofing on the Internet. A key feature of our scheme is that it does not require global routing information.  IDPFs are constructed from the information implicit in Border Gateway Protocol (BGP) route updates and are deployed in network border routers.  We establish the conditions under which the IDPF framework correctly works in that it does not discard packets with valid source addresses. We show that, even with partial deployment on the Internet, IDPFs can proactively limit the spoofing capability of attackers. In addition, they can help localize the origin of an attack packet to a small number of candidate networks

Magnetoresistance and spin-transfer torque in magnetic tunnel junctions

We comment on both recent progress and lingering puzzles related to research on magnetic tunnel junctions (MTJs). MTJs are already being used in applications such as magnetic-field sensors in the read heads of disk drives, and they may also be the first device geometry in which spin-torque effects are applied to manipulate magnetic dynamics, in order to make nonvolatile magnetic random access memory. However, there remain many unanswered questions about such basic properties as the magnetoresistance of MTJs, how their properties change as a function of tunnel-barrier thickness and applied bias, and what are the magnitude and direction of the spin-transfer-torque vector induced by a tunnel current.Comment: 37 pages, 2 figures. Contribution to a collection of "Current Perspectives" articles on spin transfer torque now available in the Journal of Magnetism and Magnetic Material

Magnetic tunnel junctions

No abstract

Co72Fe20B8 : structure, magnetism, and tunneling spin polarization

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

Tunneling spin polarization and annealing of Co72Fe20B8

We present measurements of tunneling spin polarization (TSP) of Co72Fe20B8 alloys in Al/Al2O3/Co72Fe20B8 tunnel junctions to further unravel the role of crystn. of the CoFeB electrodes. Whereas the TSP of films of a few hundred A ngstrom is rather insensitive to anneals up to 500 C , a 50 A film shows a strong redn. of TSP. It is hypothesized that these differences are related to a rather inhomogeneous crystn. of the Co72Fe20B8. Magneto-optical Kerr-effect measurement on 300 A thick CoFeB wedges are used to relate the measured coercivity to these crystn. processes