Spin-dependent band structure, Fermi surface, and carrier lifetime of permalloy

Angle-resolved photoemission is used to determine the energy bands of perma lloy (Ni0.8Fe0.2) and compare them to Ni, Co, and Cu. The energy and moment um resolution (approximate to 0.01 eV and approximate to 0.01 Angstrom(-1)) is high enough to resolve the magnetically split bands at the Fermi level that are responsible for spin-dependent conductivity and tunneling. For the Sigma(1) band we find the magnetic exchange splittings delta E-ex = 0.27 e V (0.23 eV for Ni), delta k(ex) = 0.16 +/- 0.02 Angstrom(-1) (0.12 +/- 0.01 Angstrom(-1) for Ni), the Fermi velocity upsilon(F up arrow) = (0.22 +/- 0 .02) 10(6) m/s (0.28 x 10(6) m/s for Ni, 0.33 x 10(6) m/s for fcc Co), and the widths delta k(up arrow) less than or equal to 0.11 Angstrom(-1) and de lta k(down arrow) = 0.24 Angstrom(-1). Compared to Ni, permalloy features a 27% larger magnetic splitting of the Fermi surface and an extremely short mean free path of 4-8 Angstrom for minority spins. (C) 1998 American Instit ute of Physics. [S0003-6951(98)01249-2].