In itinerant electron ferromagnets, spectral weight is transferred at finite temperatures from quasiparticle peaks located at majority-and minority-spin band energies to shadow-band peaks. For a given Bloch wave vector and band index, the majority-spin shadow-band peak is located near the minority-spin quasiparticle energy and the minority-spin shadow-band peak is located near the majorityspin quasiparticle energy. This property can explain much of the temperature dependence seen in the magnetoresistance of magnetic tunnel junctions. [S0031-9007(98)06624-1]
The two-dimensional interacting electron gas at Landau level filling factor
$\nu =1$ and temperature $T=0$ is a strong ferromagnet; all spins are
completely aligned by arbitrarily weak Zeeman coupling. We report on a
theoretical study of its thermodynamic properties using a many-body
perturbation theory approach and concentrating on the recently measured
temperature dependence of the spin magnetization. We discuss the interplay of
collective and single-particle aspects of the physics and the opportunities for
progress in our understanding of itinerant electron ferromagnetism presented by
quantum Hall ferromagnets.Comment: REVTex, 10 pages, 3 uuencoded, compressed and tarred PostScript
figures appende
The various proposals for fractional-quantum-Hall-effect quasielectron trial wave functions are reconsidered. In a short-range model for the electronic interaction, the energy expectation values of four different trial wave functions are calculated at filling factorfor up to ten electrons in the disk geometry. Jain s trial wave function displays the lowest-energy expectation value.It is by now generally accepted that the fractional quantum Hall effect (FQHE) arises due to peculiar features of the multiparticle energy spectrum of interacting, spin-polarized electrons moving in two dimensions under the inHuence of a strong, perpendicular magnetic field. These peculiarities appear at definite filling factors v (electronic densities). Best understood are the ground states at filling factors v = -(q odd). Here, the Laughlin wave function is not only a good trial wave function, but also an exact solution of a special shortrange two-particle interaction.Quasiparticles were in-
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