2,539 research outputs found
Airy-function electron localization in the oxide superlattices
Oxide superlattices and microstructures hold the promise for creating a new
class of devices with unprecedented functionalities. Density-functional studies
of the recently fabricated superlattices of lattice-matched perovskite
titanates (SrTiO3)n/(LaTiO3)m reveal a classic wedge-shaped potential
originating from the Coulomb potential of a charged sheet of La atoms. The
potential in turn confines the electrons in the vicinity of the sheet, leading
to an Airy-function localization of the electron states. Magnetism is
suppressed for structures with a single LaTiO3 monolayer, while the bulk
antiferromagnetism is recovered in the structures with a thicker LaTiO3, with a
narrow transition region separating the magnetic LaTiO3 and the non-magnetic
SrTiO3
On the Ruderman-Kittel-Kasuya-Yosida interaction in graphene
The two dimensionality plus the linear band structure of graphene leads to
new behavior of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, which is
the interaction between two magnetic moments mediated by the electrons of the
host crystal. We study this interaction from linear response theory. There are
two equivalent methods both of which may be used for the calculation of the
susceptibility, one involving the integral over a product of two Green's
functions and the second that involves the excitations between occupied and
unoccupied states, which was followed in the original work of Ruderman and
Kittel. Unlike the behavior of an
ordinary two-dimensional (2D) metal, in graphene falls off as ,
shows the -type of behavior, which contains
an interference term between the two Dirac cones, and it oscillates for certain
directions and not for others. Quite interestingly, irrespective of any
oscillations, the RKKY interaction in graphene is always ferromagnetic for
moments located on the same sublattice and antiferromagnetic for moments on the
opposite sublattices, a result that follows from particle-hole symmetry.Comment: 12 pages, 5 figures, submitted to AIP Conference Proceeding
Ferrodistorsive orbital ordering in the layered nickelate NaNiO_2: A density-functional study
The electronic structure and magnetism in the sodium nickelate NaNiO_2 in the
low-temperature phase is studied from density-functional calculations using the
linear muffin-tin orbitals method. An antiferromagnetic solution with a
magnetic moment of 0.7 m_B per Ni ion is found. A ferrodistorsive orbital
ordering is shown to occur due to the Jahn-Teller distortion around the Ni^{3+}
ion in agreement with the orbital ordering inferred from neutron diffraction.
While the intralayer exchange is ferromagnetic, the interlayer exchange is
weakly antiferromagnetic, mediated by a long Ni-O-Na-O-Ni superexchange path.Comment: 4 pages, 5 figures Submitted to MMM2004 conference Proceeding
Two Dimensional Spin-Polarized Electron Gas at the Oxide Interfaces
The formation of a novel spin-polarized 2D electron gas at the LaMnO
monolayer embedded in SrMnO is predicted from the first-principles
density-functional calculations. The La (d) electrons become confined in the
direction normal to the interface in the potential well of the La layer,
serving as a positively-charged layer of electron donors. These electrons
mediate a ferromagnetic alignment of the Mn t spins near the interface
via the Anderson-Hasegawa double exchange and become, in turn, spin-polarized
due to the internal magnetic fields of the Mn moments.Comment: 5 pages, 6 figure
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