421 research outputs found
On the Coexistence in RuSr2GdCu2O8 of Superconductivity and Ferromagnetism
We review the reasons that make superconductivity unlikely to arise in a
ferromagnet. Then, in light of the report by Tallon and collaborators that
RuSr2GdCu2O8 becomes superconducting at approximately 35 K which is well below
the Curie temperature of 132 K, we consider whether the objections really apply
to this compound. Our considerations are supported by local spin density
calculations for this compound, which indeed indicate a ferromagnetic RuO2
layer. The Ru moment resides in t_2g orbitals but is characteristic of
itinerant magnetism (and is sensitive to choice of exchange-correlation
potential and to the atomic positions). Based on the small exchange splitting
that is induced in the Cu-O layers, the system seems capable of supporting
singlet superconductivity an FFLO-type order parameter and possibly a pi-phase
alternation between layers. If instead the pairing is triplet in the RuO2
layers, it can be distinguished by a spin-polarized supercurrent. Either type
of superconductivity seems to imply a spontaneous vortex phase if the
magnetization is rotated out of the plane.Comment: 3 revtex pages, 2 embedded figures. In press, Proc. HTS99 Conf.,
Miami, 199
Theoretical Study on Coexistence of Ferromagnetism and Superconductivity
On the basis of a two-dimensional t-t' Hubbard model in ferromagnetic and
paramagnetic states, the triplet superconducting mechanism is investigated by
the third-order perturbation theory with respect to the on-site Coulomb
interaction U. In general, the superconducting state is more stable in the
paramagnetic state than in the ferromagnetic state. As a special case, the
dominant ferromagnetic superconductivity is obtained by the electron-electron
correlation between the electronlike majority and holelike minority bands.
Furthermore, it is pointed out that in some cases the two bands play an
essential role for the coexistence of superconductivity and ferromagnetism.Comment: 5 pages, 10 figure
Unified character of correlation effects in unconventional Pu-based superconductors and \delta-Pu
Electronic structure calculations combining the local-density approximation
with an exact diagonalization of the Anderson impurity model show an
intermediate 5f^5-5f^6-valence ground state and delocalization of the 5f^5
multiplet of the Pu atom 5f-shell in PuCoIn_5, PuCoGa_5, and \delta-Pu. The
5f-local magnetic moment is compensated by a moment formed in the surrounding
cloud of conduction electrons. For PuCoGa_5 and \delta-Pu the compensation is
complete and the Anderson impurity ground state is a singlet. For PuCoIn_5 the
compensation is partial and the Pu ground state is magnetic. We suggest that
the unconventional d-wave superconductivity is likely mediated by the 5f-states
antiferromagnetic fluctuations in PuCoIn_5, and by valence fluctuations in
PuCoGa_5.Comment: 5 pages, 3 figure
Magnetoelastic mechanism of spin-reorientation transitions at step-edges
The symmetry-induced magnetic anisotropy due to monoatomic steps at strained
Ni films is determined using results of first - principles relativistic
full-potential linearized augmented plane wave (FLAPW) calculations and an
analogy with the N\'eel model. We show that there is a magnetoelastic
anisotropy contribution to the uniaxial magnetic anisotropy energy in the
vicinal plane of a stepped surface. In addition to the known spin-direction
reorientation transition at a flat Ni/Cu(001) surface, we propose a
spin-direction reorientation transition in the vicinal plane for a stepped
Ni/Cu surface due to the magnetoelastic anisotropy. We show that with an
increase of Ni film thickness, the magnetization in the vicinal plane turns
perpendicular to the step edge at a critical thickness calculated to be in the
range of 16-24 Ni layers for the Ni/Cu(1,1,13) stepped surface.Comment: Accepted for publication in Phys. Rev.
Subgingival Curettage Versus Surgical Elimination of Periodontal Pockets
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142057/1/jper0167.pd
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