376 research outputs found
Resistive relaxation in field-induced insulator-metal transition of a (LaPr)SrMnO bilayer manganite single crystal
We have investigated the resistive relaxation of a
(LaPr)SrMnO single crystal, in
order to examine the slow dynamics of the field-induced insulator to metal
transition of bilayered manganites. The temporal profiles observed in remanent
resistance follow a stretched exponential function accompanied by a slow
relaxation similar to that obtained in magnetization and magnetostriction data.
We demonstrate that the remanent relaxation in magnetotransport has a close
relationship with magnetic relaxation that can be understood in the framework
of an effective medium approximation by assuming that the first order parameter
is proportional to the second order one.Comment: 6 pages,5 figure
Stretched exponential behavior in remanent lattice striction of a (La,Pr)SrMnO bilayer manganite single crystal
We have investigated the time dependence of remanent magnetostriction in a
(La,Pr)SrMnO single crystal, in order to examine
the slow dynamics of lattice distortion in bilayered manganites. A competition
between double exchange and Jahn-Teller type orbital-lattice interactions
results in the observed lattice profile following a stretched exponential
function. This finding suggests that spatial growth of the local lattice
distortions coupled with e-electron orbital strongly correlates with the
appearance of the field-induced CMR effect.Comment: 3 figure
Ferromagnetism at 300 K in spin-coated anatasea and rutile Ti0.95Fe0.05O2 films
Thin films of Ti1-xFexO2 (x=0 and 0.05) have been prepared on sapphire
substrates by spin-on technique starting from metal organic precursors. When
heat treated in air at 550 and 700 degrees C respectively, these films present
pure anatase and rutile structures as shown both by X-ray diffraction and Raman
spectroscopy. Optical absorption indicate a high degree of transparency in the
visible region. Such films show a very small magnetic moment at 300 K. However,
when the anatase and the rutile films are annealed in a vacuum of 1x10-5 Torr
at 500 degrees C and 600 degrees C respectively, the magnetic moment, at 300 K,
is strongly enhanced reaching 0.46 B/Fe for the anatase sample and 0.48
B/Fe for the rutile one. The ferromagnetic Curie temperature of these
samples is above 350 K.Comment: 13 october 200
Does EELS haunt your photoemission measurements?
It has been argued in a recent paper by R. Joynt (R. Joynt, Science 284, p
777 (1999)) that in the case of poorly conducting solids the photoemission
spectrum close to the Fermi Energy may be strongly influenced by extrinsic loss
processes similar to those occurring in High Resolution Electron Energy Loss
Spectroscopy (HR-EELS), thereby obscuring information concerning the density of
states or one electron Green's function sought for. In this paper we present a
number of arguments, both theoretical and experimental, that demonstrate that
energy loss processes occurring once the electron is outside the solid,
contribute only weakly to the spectrum and can in most cases be either
neglected or treated as a weak structureless background.Comment: 6 pages, figures included. Submitted to PR
Effect of suppression of local distortion on magnetic, electrical and thermal transport properties of Cr substituted bi-layer manganite LaSrMnO
We have investigated magnetic, electrical and thermal transport properties
(Seebeck effect and thermal conductivity) of
LaSrMnCrO polycrystalline samples (=0.1, 0.2, 0.4
and 0.6). The Cr substitution for Mn sites causes a removal of
orbital of -electron resulting in a volume shrinkage of
lattice. Magnetic measurements reveal the appearance of a glassy behavior for
Cr-doped samples, accompanied by both a collapse of the A-type
antiferromagnetic structure and the growth of ferromagnetic clusters. Cr-doping
effect on electrical transport strongly enhances an insulating behavior over a
wide range of temperature, while it suppresses a local minimum of
thermoelectric power at lower temperatures. The phonon thermal conduction
gradually rises with increasing Cr content, which is contradictory to a typical
impurity effect on thermal conductivity. We attribute this to a suppression of
local lattice distortion through the introduction of Jahn-Teller inactive ions
of Cr.Comment: 8 pages, 9figure
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