M. Hochstrasser

Enhanced spin polarization of conduction electrons in Ni explained by comparison with Cu

The spin-split Fermi-level crossings of the conduction band in Ni are mapped out by high-resolution photoemission and compared to the equivalent crossing in Cu. The area of the quasiparticle peak decreases rapidly below EF in Ni, but not in Cu. Majority spins have larger spectral weight at EF than minority spins, thereby enhancing the spin polarization beyond that expected from the density-of-states. A large part of the effect can be traced to a rapid variation of the matrix element with k at the point where the s, p band begins to hybridize with the dz state. However, it is quite possible that the intensity drop in Ni is reinforced by a transfer of spectral weight from single-particle to many-electron excitations. The results suggest that the matrix element should be considered for explaining the enhanced spin polarization observed for Ni in spin-polarized tunneling.

On the magnetic instability of ultrathin FCC FexNi1-x films

Abstract The `invar effect’ in Fe x Ni 1− x alloys occurs when the Fe content approaches 65%. At this point, the magnetization falls to zero, and a martensitic structural transformation from an FCC to BCC lattice occurs. This paper addresses the question: what happens if this structural transformation is suppressed in an ultrathin alloy film?

Fermi surface study of pseudomorphic Fe1−xNix and Co1−xNix thin films on Cu(100)

We report angle resolved photoemission studies of the electronic behavior of ultrathin epitaxial layers of fcc structured binary alloys, Fe1−xNix and Co1−xNix, deposited by molecular beam epitaxy on Cu(100) substrates. In particular, we have used Fermi surface mapping to monitor changes in the Fermi surface with increasing magnetization density. Fe1−xNix and Co1−xNix binary alloys show a different behavior in the bulk. Co1−xNix is structurally and magnetically well-behaved. In particular, the magnetic moment varies linearly as a function of concentration. This is in sharp contrast to fcc Fe1−xNix which displays a magnetic instability at ∼65% Fe content. An extended regime of fcc stability is possible via epitaxy on Cu(100). The changes in the Fermi surfaces of Fe1−xNix and Co1−xNix pseudomorphic film alloys depending on various concentrations of Ni have been investigated in a large photon energy regime. We address the following question: To what degree is the Fermi surface sharply preserved in substitutio...