46 research outputs found
Evidence for charge orbital and spin stripe order in an overdoped manganite
We present diffraction data on a single-layered manganite
La(0.42)Sr(1.58)MnO4 with hole doping (x>0.5). Overdoped La(0.42)Sr(1.58)MnO4
exhibits a complex ordering of charges, orbitals and spins. Single crystal
neutron diffraction experiments reveal three incommensurate and one
commensurate order parameters to be tightly coupled. The position and the shape
of the distinct superstructure scattering points to a stripe arrangement in
which ferromagnetic zigzag chains are disrupted by additional Mn4+ stripes
Orbital polaron lattice formation in lightly doped La1-xSrxMnO3
By resonant x-ray scattering at the Mn K-edge on La7/8Sr1/8MnO3, we show that
an orbital polaron lattice (OPL) develops at the metal-insulator transition of
this compound. This orbital reordering explains consistently the unexpected
coexistence of ferromagnetic and insulating properties at low temperatures, the
quadrupling of the lattice structure parallel to the MnO2-planes, and the
observed polarization and azimuthal dependencies. The OPL is a clear
manifestation of strong orbital-hole interactions, which play a crucial role
for the colossal magnetoresistance effect and the doped manganites in general
Orbiton-mediated multi-phonon scattering in LaSrMnO
We report on Raman scattering measurements of single crystalline
LaSrMnO (=0, 0.06, 0.09 and 0.125), focusing on the high
frequency regime. We observe multi-phonon scattering processes up to
fourth-order which show distinct features: (i) anomalies in peak energy and its
relative intensity and (ii) a pronounced temperature-, polarization-, and
doping-dependence. These features suggest a mixed orbiton-phonon nature of the
observed multi-phonon Raman spectra.Comment: 6pages, 6figures, submitted to PR
Pressure-induced melting of the orbital polaron lattice in La1-xSrxMnO3
We report on the pressure effects on the orbital polaron lattice in the
lightly doped manganites , with . The
dependence of the orbital polaron lattice on chemical pressure is
studied by substituting Pr for La in
. In addition, we have studied
its hydrostatic pressure dependence in
. Our results strongly
indicate that the hopping significantly contributes to the stabilization of
the orbital polaron lattice and that the orbital polarons are ferromagnetic
objects which get stabilized by local double exchange processes. The analysis
of short range orbital correlations and the verification of the Grueneisen
scaling by hard x-ray, specific heat and thermal expansion data reinforces our
conclusions.Comment: 7 figure
Crystal and magnetic structure of La_{1-x}Sr_{1+x}MnO_{4} : role of the orbital degree of freedom
The crystal and magnetic structure of La_{1-x}Sr_{1+x}MnO_4 (0<x<0.7) has
been studied by diffraction techniques and high resolution capacitance
dilatometry. There is no evidence for a structural phase transition like those
found in isostructural cuprates or nickelates, but there are significant
structural changes induced by the variation of temperature and doping which we
attribute to a rearrangement of the orbital occupation.Comment: 8 pages, 6 figures, submitted to PR
Existence of orbital polarons in ferromagnetic insulating LaSrMnO (0.110.14) evidenced by giant phonon softening
We present an inelastic light scattering study of single crystalline
(LaPr)SrMnO (, and
,). A giant softening up to 20 - 30 cm of the
Mn-O breathing mode has been observed only for the ferromagnetic insulating
(FMI) samples () upon cooling below the Curie
temperature. With increasing Pr-doping the giant softening is gradually
suppressed. This is attributed to a coupling of the breathing mode to orbital
polarons which are present in the FMI phase.Comment: 4 pages, 5 figure
Π£ΡΡΠΎΠΉΡΠΈΠ²ΠΎΡΡΡ Π±ΠΎΡΡΠΎΠ² ΠΊΠ°ΡΡΠ΅ΡΠΎΠ² Π² ΡΠ»ΠΎΠΆΠ½ΠΎΡΡΡΡΠΊΡΡΡΠ½ΠΎΠΌ ΠΌΠ°ΡΡΠΈΠ²Π΅ ΠΌΡΠ³ΠΊΠΈΡ ΠΏΠΎΡΠΎΠ΄
ΠΠ·Π»ΠΎΠΆΠ΅Π½Ρ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ, Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ ΠΊΠΎΡΠΎΡΡΡ
Π±ΡΠ»ΠΈ ΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½Ρ
Π³Π΅ΠΎΠΌΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΈΠ΅ Π·Π°ΠΊΠΎΠ½ΠΎΠΌΠ΅ΡΠ½ΠΎΡΡΠΈ ΡΡΡΠΎΠΉΡΠΈΠ²ΠΎΠ³ΠΎ ΡΠΎΡΡΠΎΡΠ½ΠΈΡ ΠΎΡΠΊΠΎΡΠΎΠ² ΠΈ Π±ΠΎΡΡΠΎΠ²
ΠΊΠ°ΡΡΠ΅ΡΠΎΠ² Ρ ΡΡΠ΅ΡΠΎΠΌ ΡΠ»ΠΎΠΆΠ½ΠΎΠΉ Π³Π΅ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΡΡΡΠΊΡΡΡΡ, Π³ΠΈΠ΄ΡΠΎΠ³Π΅ΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΡ
Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊ ΠΈ Π½Π°Π³ΡΡΠ·ΠΎΠΊ Π³ΠΎΡΠ½ΠΎ-ΡΡΠ°Π½ΡΠΏΠΎΡΡΠ½ΠΎΠ³ΠΎ ΠΎΠ±ΠΎΡΡΠ΄ΠΎΠ²Π°Π½ΠΈΡ.
ΠΠ°ΡΠ΅ΡΠΈΠ°Π» ΠΌΠΎΠ½ΠΎΠ³ΡΠ°ΡΠΈΠΈ ΠΌΠΎΠΆΠ΅Ρ Π±ΡΡΡ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ Π² ΡΡΠ΅Π±Π½ΠΎΠΌ ΠΏΡΠΎΡΠ΅ΡΡΠ΅ ΠΏΡΠΈ
ΠΈΠ·Π»ΠΎΠΆΠ΅Π½ΠΈΠΈ Π»Π΅ΠΊΡΠΈΠΉ ΠΏΠΎ Π΄ΠΈΡΡΠΈΠΏΠ»ΠΈΠ½Π°ΠΌ Β«ΠΠ΅Ρ
Π°Π½ΠΈΠΊΠ° Π³ΡΡΠ½ΡΠΎΠ²Β», Β«ΠΠ΅Ρ
Π°Π½ΠΈΠΊΠ° Π³ΠΎΡΠ½ΡΡ
ΠΏΠΎΡΠΎΠ΄Β», Β«ΠΡ
ΡΠ°Π½Π° Π·Π΅ΠΌΠ½ΠΎΠΉ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈΒ», ΠΏΡΠΈ ΠΈΠ·ΡΡΠ΅Π½ΠΈΠΈ Π²ΠΎΠΏΡΠΎΡΠΎΠ²
Π³Π΅ΠΎΠΌΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΎΡΠ΅Π½ΠΊΠΈ ΡΡΡΠΎΠΉΡΠΈΠ²ΠΎΡΡΠΈ Π΅ΡΡΠ΅ΡΡΠ²Π΅Π½Π½ΡΡ
ΠΈ ΡΠ΅Ρ
Π½ΠΎΠ³Π΅Π½Π½ΡΡ
ΠΎΡΠΊΠΎΡΠΎΠ²,
ΠΏΡΠΎΠ³Π½ΠΎΠ·Π° ΠΎΠΏΠΎΠ»Π·Π½Π΅ΠΎΠΏΠ°ΡΠ½ΡΡ
ΡΠΈΡΡΠ°ΡΠΈΠΉ, Π΄Π»Ρ Π΄Π°Π»ΡΠ½Π΅ΠΉΡΠ΅ΠΉ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠΊΠΈ ΠΈ
ΡΡΠΎΠ²Π΅ΡΡΠ΅Π½ΡΡΠ²ΠΎΠ²Π°Π½ΠΈΡ ΠΌΠ΅ΡΠΎΠ΄ΠΎΠ² Π°Π½Π°Π»ΠΈΠ·Π° Π½Π°ΠΏΡΡΠΆΠ΅Π½Π½ΠΎ-Π΄Π΅ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ
ΡΠΎΡΡΠΎΡΠ½ΠΈΡ ΠΌΠ°ΡΡΠΈΠ²Π° ΠΌΡΠ³ΠΊΠΈΡ
Π²ΡΠΊΡΡΡΠ½ΡΡ
ΠΏΠΎΡΠΎΠ΄, Π° ΡΠ°ΠΊΠΆΠ΅ ΡΠΏΠ΅ΡΠΈΠ°Π»ΠΈΡΡΠ°ΠΌΠΈ Π½Π°ΡΡΠ½ΠΎ-
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°ΡΠ΅Π»ΡΡΠΊΠΈΡ
ΡΡΡΠ΅ΠΆΠ΄Π΅Π½ΠΈΠΉ Π΄Π»Ρ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠΊΠΈ ΠΏΡΠΎΠ΅ΠΊΡΠ½ΠΎΠΉ Π΄ΠΎΠΊΡΠΌΠ΅Π½ΡΠ°ΡΠΈΠΈ
Evidence for a Low-Spin to Intermediate-Spin State Transition in LaCoO3
We present measurements of the magnetic susceptibility and of the thermal
expansion of a LaCoO single crystal. Both quantities show a strongly
anomalous temperature dependence. Our data are consistently described in terms
of a spin-state transition of the Co ions with increasing temperature
from a low-spin ground state to an intermediate-spin state without (100K -
500K) and with (>500K) orbital degeneracy. We attribute the lack of orbital
degeneracy up to 500K to (probably local) Jahn-Teller distortions of the
CoO octahedra. A strong reduction or disappearance of the Jahn-Teller
distortions seems to arise from the insulator-to-metal transition around 500 K.Comment: an error in the scaling factor of Eq.(4) and consequently 2 values of
table I have been corrected. The conclusions of the paper remain unchanged.
See also: C. Zobel et al. Phys. Rev. B 71, 019902 (2005) and J. Baier et al.
Phys. Rev. B 71, 014443 (2005
Bridging charge-orbital ordering and Fermi surface instabilities in half-doped single-layered manganite La_0.5Sr_1.5MnO_4
Density waves are inherent to the phase diagrams of materials that exhibit
unusual, and sometimes extraordinarily useful properties, such as
superconductivity and colossal magnetoresistance. While the pure charge density
waves (CDW) are well described by an itinerant approach, where electrons are
treated as waves propagating through the crystal, the charge-orbital ordering
(COO) is usually explained by a local approach, where the electrons are treated
as localized on the atomic sites. Here we show that in the half-doped manganite
La0.5Sr1.5MnO4 (LSMO) the electronic susceptibility, calculated from the
angle-resolved photoemission spectra (ARPES), exhibits a prominent
nesting-driven peak at one quarter of the Brillouin zone diagonal, that is
equal to the reciprocal lattice vector of the charge-orbital pattern. Our
results demonstrate that the Fermi surface geometry determines the propensity
of the system to form a COO state which, in turn, implies the applicability of
the itinerant approach also to the COO