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1.
A.-L. Barra G. Chouteau A. Stepanov A. Rougier C. Delmas 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):551-562
compounds have a layered structure made of alternating Ni-O and Li-O slabs. An amount z of extra divalent Ni ions is always present in the Li-O layers. We show, using high field magnetisation, static and dynamic
susceptibility and high frequency ESR, that the magnetic properties are driven by the z parameter. The compounds can be described as ferromagnetic Ni-O layers, bridged by clusters possessing a net ferromagnetic
moment.
Received: 24 July 1998 / Revised and Accepted: 23 September 1998 相似文献
2.
H. He W. Y. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(4):457-463
The spin-states of cobalt based perovskite compounds depend sensitively
on the valence state and local crystal environment of Co ions and the
rich physical properties arise from strong coupling among charge, spin,
and orbital degrees of freedom. While extensive studies have been carried
out in the past, most of them concentrated on the isotropic compound
LaCoO3. In this paper, using the unrestricted Hartree-Fock approximation
and the real-space recursion method, we have investigated the competition
of various magnetically ordered spin-states of anisotropic double-layered
perovskite Sr2Y0.5Ca0.5Co2O7. The energy
comparison among these states shows that the nearest-neighbor
high-spin-intermediate-spin ferromagnetically ordered state is the relevant
magnetic ground state of the compound. The magnetic structure and sizes of
magnetic moments are consistent with the recent experimental observation. 相似文献
3.
D. P. Kozlenko S. V. Trukhanov E. V. Lukin I. O. Troyanchuk B. N. Savenko 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):361-365
The crystal and magnetic structures of the oxygen deficient manganites
La0.7Sr0.3MnO3-d (d = 0.15, 0.20) have been studied by means
of powder neutron diffraction over the 0–5.2 GPa pressure and 10–290 K
temperature ranges. La0.7Sr0.3MnO2.85 exhibits a coexistence
of rhombohedral
and tetragonal (I4/mcm) crystal structures and below
Tg ~ 50 K a spin glass state is formed.
La0.7Sr0.3MnO2.80 exhibits a tetragonal (I4/mcm) crystal structure.
Below Tg ~ 50 K a phase separated magnetic state is formed,
involving coexistence of C-type AFM domains with spin glass domains. In both
compounds the crystal structure and magnetic states remain stable upon
compression. The factors leading to the formation of different magnetic
states in La0.7Sr0.3MnO3-d (d = 0.15, 0.20) and their specific
high pressure behavior, contrasting with that of the stoichiometric
A0.5Ba0.5MnO3 (A = Nd, Sm) compounds showing pressure-induced
suppression of the spin glass state and the appearance of the FM state, are analysed. 相似文献
4.
S. K. Dhar P. Manfrinetti M. L. Fornasini P. Bonville 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):187-192
170Yb M?ssbauer spectroscopy, temperature dependent X-ray,
magnetisation and specific heat data are presented in the hexagonal
intermetallic YbAl3C3, in order to shed light on the isostructural
transition occurring near 80 K and
to investigate the electronic state of the Yb ion above and below the
transition. In the low temperature phase, we find that there occurs an atomic
rearrangement in the hexagonal unit cell, leading to a strong symmetry
lowering at the Yb site. We show that no magnetic ordering of the Yb3+
moments occurs down to 0.04 K, and we discuss this finding in terms of
4f-conduction electron hybridisation and geometric frustration. 相似文献
5.
N. Shannon T. Chatterji F. Ouchni P. Thalmeier 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):287-297
We construct a theory of spin wave excitations in the bilayer manganite La1.2Sr1.8Mn2O7 based on the simplest possible double-exchange model, but including leading quantum corrections to the spin wave dispersion
and damping. Comparison is made with recent inelastic neutron scattering experiments. We find that quantum effects account
for some part of the measured damping of spin waves, but cannot by themselves explain the observed softening of spin waves
at the zone boundary. Furthermore a doping dependence of the total spin wave dispersion and the optical spin wave gap is predicted.
Received 15 January 2002 Published online 6 June 2002 相似文献
6.
V. M. Zainullina M. A. Korotin V. L. Kozhevnikov 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(4):425-431
The electronic structure of strontium ferrite Sr3Fe2O6 was
calculated using the tight-binding linear muffin-tin orbital method (TB
LMTO) in the local spin density approximation of density functional theory
with Coulomb correlations correction (LSDA+U). The semiconducting character
of the spectrum with charge transfer energy gap of 1.82 eV was obtained in
reasonably good agreement with experimental data. The iron ions are found
to be in the high spin state. The calculated value of the local spin
magnetic moment of Fe3+ ion is 3.94 μB which is not typical for
trivalent iron ion in the high spin state. It is shown that the strong
hybridization between Fe3d and O2p orbitals favors the
d6 L configuration of Fe3+ ion, where L is a hole in the oxygen p shell. The mechanism of oxygen transport in ferrite is discussed basing on the total energy calculations of the
different spatial configurations of oxygen vacancies. 相似文献
7.
A. Sundaresan J.L. Tholence A. Maignan C. Martin M. Hervieu B. Raveau E. Suard 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(3):431-438
Neutron and electron diffraction, electrical transport and magnetic measurements have been carried out on a newly synthesized
electron doped Sr1-xCe
x
MnO3 (x = 0.1, 0.2, 0.3 and 0.4) system. For x=0.1, while cooling, it undergoes a first-order metal-insulator transition at 315 K which is associated with a structural
transition from cubic (Pm3m) to tetragonal (I4/mcm) due to Jahn-Teller ordering () which stabilizes a chain like (C-type) antiferromagnetic ground state with . The antiferromagnetic insulator state is insensitive to an applied magnetic field of 7 T. With increase of x, while the nuclear structure at room temperature for x=0.2 and 0.3 remains tetragonal, for x=0.4 it becomes orthorhombic (Imma) where the doping electrons seem to occupy mainly the d
x2-y2 symmetry. Further, the JT distortion and the antiferromagnetic interactions decrease with doping and a small negative magnetoresistance
appears for . Magnetic measurements show that the dilution of antiferromagnetic interaction results into a spin glass like behaviour at
low temperature for the samples with x=0.3 and 0.4. This behaviour is in contrast with the CMR properties of calcium based electron doped systems and hole doped
manganites. The stability of C-type antiferromagnetic ordering in the electron doped system with large A-site cationic size
may be responsible for the absence of double exchange ferromagnetism and CMR effect.
Received 10 September 1999 相似文献
8.
J.W. Taylor T.J. Smith K.H. Andersen H. Capellmann R.K. Kremer A. Simon O. Schärpf K.-U. Neumann K.R.A. Ziebeck 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(2):199-207
The magnetic response in V
2
O
3
has been investigated using polarised neutron scattering with polarisation analysis. Measurements were carried out at three
temperatures corresponding to the antiferromagnetic insulating ground state, the metallic phase and the high temperature metallic
phase. At the first order metal insulator transition there is a dramatic change in the magnetic response with the metallic
and high temperature metallic phases being characterised by ferromagnetic spatial correlations of the paramagnetic response.
The establishment of ferromagnetic correlations at the metal insulator transition accounts for the abrupt jump in the uniform
susceptibility. It is proposed that the differentiation of the V-V distances across the edges of VO
6
octahedra is of critical importance for the change in electronic conductivity but also for the establishment of the spatial
correlations. The gradual high temperature evolution of the conductivity then occurs by the reduction in the vanadium d overlap
brought about by thermal expansion. The first order reduction in atomic volume which occurs on the establishment of the metallic
phase results from an instability of the vanadium local moment arising from the change in electronic structure.
Received 7 April 1999 相似文献
9.
J. Strempfer Th. Brückel W. Caliebe A. Vernes H. Ebert W. Prandl J.R. Schneider 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(1):63-72
Results of high-energy magnetic X-ray diffraction on pure antiferromagnetic chromium are presented. The temperature dependence
of the propagation vector of the spin-density wave (SDW) and the strain-wave (SW) could be reproduced. The temperature dependence
of the magnetic integrated intensity could be measured in the transversally as well as in the longitudinally polarised SDW
phase. The magnetic form-factor has been determined in the transversally polarised SDW phase with five magnetic satellites.
For the first time a spin-orbit separation has been performed by comparing X-ray to neutron data. The small orbital contribution
to the magnetisation density turns out to be negligible, in agreement to our relativistic band-structure calculations. In
addition, measurements of strain-wave reflections have been undertaken, and the results complement previous studies.
Received 17 August 1998 and Received in final form 10 August 1999 相似文献
10.
A. Liebsch H. Ishida 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(4):405-411
There exists presently considerable debate over the question whether
local Coulomb interactions can explain the absence of the small e′
g
Fermi surface hole pockets in photoemission studies of Na0.3CoO2.
By comparing dynamical mean field results for different single particle
Hamiltonians and exact diagonalization as well as quantum Monte Carlo
treatments, we show that, for realistic values of the Coulomb energy U
and Hund exchange J, the e′
g pockets can be slightly enhanced or
reduced compared to band structure predictions, but they do not disappear. 相似文献
11.
J. Goulon A. Rogalev F. Wilhelm N. Jaouen C. Goulon-Ginet Ch. Brouder 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(2):169-184
We discuss the physical content of X-ray Detected Magnetic Resonance (XDMR), i.e. a novel spectroscopy which uses XMCD to
probe the resonant precession of the local magnetization in a strong microwave pump field. We focus on the simplest case of
a steady-state precession of elemental moments in the non-linear regime of angular foldover. Like XMCD, XDMR is element and
edge selective and could become a unique tool to investigate how precessional dynamics can locally affect the spin and orbital
magnetization of p- or d-projected DOS. This should be possible only in the limit where there is no overdamping due to ultrafast
orbit-lattice relaxation. 相似文献
12.
V.I. Nizhankovskii A.I. Khar'kovskii A.J. Zaleski 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(4):761-766
Spontaneous magnetisation of (100) and (010) surfaces of single crystal MnF2 in the antiferromagnetic state has been discovered. The sign of the surface magnetisation is determined by the difference
in dielectric constants of MnF2 and ambient matter: magnetisation is directed to the substance with smaller .
Received 28 August 1998 and Received in final form 15 December 1998 相似文献
13.
D. Mannix P.C. de Camargo C. Giles A.J.A. de Oliveira F. Yokaichiya C. Vettier 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(1):19-25
We report on X-ray magnetic diffraction studies of the spin density wave antiferromagnetism formed in the conduction electron
band of chromium. Non-resonant X-ray magnetic scattering was used to directly determine that chromium has zero orbital magnetisation.
Furthermore, the azimuthal dependence of this scattering provides unique evidence that chromium forms a linearly polarised
wave. In the vicinity of the K absorption edge, resonant X-ray magnetic scattering was observed. A consistent model of the
magnetic scattering has been derived from the resonant and non-resonant magnetic amplitudes. The enhancement of the magnetic
intensity arises primarily from dipole transitions from the core 1s level to 4p states. Quadrupole transitions to the magnetic 3d states are essentially non-existent due to their sensitivity to (and the absence of) orbital moment. This effect is predicted
from atomic considerations of the 3d5 ( = 0) transition metal ions.
Received 22 September 2000 相似文献
14.
J.-E. Jørgensen L. Keller 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(4):445-453
The crystal and magnetic structures of
Dy1-xCaxBaCo2O5.5
for x = 0.0 and 0.1 have been studied by neutron powder diffraction and the
crystal structures of both compounds were found to be best described in
space group Pmmm with a ap × 2ap × 2ap unit cells where ap is the lattice parameter
of the cubic perovskite unit cell. The a- and b-axes were found to decrease
and increase abruptly between 315 and 350 K as the temperature
increases and the unit cell volumes exhibit signs of excess thermal
expansion in the temperature range from 260 to 315 K.
Dy0.9Ca0.1BaCo2O5.5
orders antiferromagnetically for T ≤ 305 K into a G-type magnetic
structure with a 2ap × 2ap × 2ap
magnetic unit cell. DyBaCo2O5.5 exhibits two
magnetically ordered phases and a G-type magnetic structure was observed at
the investigated temperatures 260 and 290 K. A 2ap ×
2ap × 4ap magnetic unit cell was needed for
indexing of the magnetic reflections observed for T ≤ 230 K. The
low temperature magnetic structure of
DyBaCo2O5.5 is different from the observed
magnetic structures of TbBaCo2O5.5 and
HoBaCo2O5.5 despite the proximity of Tb, Dy and
Ho in the periodic table. It is a relatively complex antiferromagnetic
structure with both pyramidally and octahedrally coordinated Co ions in the
intermediate spin state. It contains both ferro- and antiferromagnetic
interactions and the magnetic moments are canted in the
a, b-plane. The canting
angles between the magnetic moments and the
b-axis are 6.6 and 50.0° at 20 K for the
pyramidally and octahedrally coordinated Co ions, respectively. The high and
low temperature magnetic phases were found to coexist at 230 K. 相似文献
15.
Y.S. Lee M. Greven B.O. Wells R.J. Birgeneau G. Shirane 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(1):15-22
We report a neutron scattering study of the instantaneous spin correlations in the two-dimensional spin S
=5/2 square-lattice Heisenberg antiferromagnet Rb2MnF4. The measured correlation lengths are quantitatively described, with no adjustable parameters, by high-temperature series
expansion results and by a theory based on the quantum self-consistent harmonic approximation. Conversely, we find that the
data, which cover the range from about 1 to 50 lattice constants, are outside of the regime corresponding to renormalized
classical behavior of the quantum non-linear model. In addition, we observe a crossover from Heisenberg to Ising critical behavior near the Néel temperature; this crossover
is well described by a mean-field model with no adjustable parameters.
Received: 3 March 1998 / Received in final form: 4 May 1998 /
Accepted: 19 May 1998 相似文献
16.
O. Toulemonde F. Studer A. Barnabé B. Raveau J.B. Goedkoop 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(2):233-240
X-ray absorption spectroscopy (XAS) and soft-X-ray magnetic circular dichroism (SXMCD) at the Mn L2,3-, Cr L2,3- and O-K edges of Sm0.5Ca0.5Mn1-xCrxO3 () bulk polycrystalline samples have been performed at T=20 K below the ferromagnetic Curie temperature. We show the existence of a magnetic sublattice on each of the probed cations.
Considering an electronically phase-separated system, results are compared with magnetization and resistivity measurements
and a tentative correlation with magnetoresistance properties on such doped compounds is discussed.
Received 7 January 2000 相似文献
17.
J.I. Espeso J. García Soldevilla J.A. Blanco J. Rodríguez Fernández J.C. Gómez Sal M.T. Fernández Díaz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):625-632
The ground state of the strongly correlated electron CeNi1-xCux compounds has been investigated by means of neutron scattering experiments. Thus, magnetic diffraction was performed for
compounds showing long-range magnetic order (x
> 0.2). An evolution from a collinear ferromagnetic structure for x
=0.6 to a simple antiferromagnetic one for CeCu takes place through some more complex magnetic structures for intermediate compositions.
The magnetic moments are continuously reduced when the Ni content increases reflecting the progressive enhancement of the
Kondo screening. The large reduction found for x
=0.6 compound is discussed and the existence of a spin glass like component of the magnetic moment cannot be discarded. From the
quasielastic spectra, we have obtained the Kondo temperatures which are close to the magnetic ordering ones. The quasielastic
line-width evolves from a linear temperature dependence to a T
1/2
behaviour when approaching the non-magnetic limit. Then, this system provides an interesting example for the evolution of
unstable 4
f shell relaxation regimes when modifying the hybridisation strength.
Received 22 May 2000 相似文献
18.
K. Hagdorn D. Hohlwein J. Ihringer K. Knorr W. Prandl H. Ritter H. Schmid Th. Zeiske 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(2):243-254
Ho0.1Ca0.9MnO3 is a canted antiferromagnet with the magnetic space group Pn
'
ma
'. The magnetic structure is a superposition C
x
F
y
A
z of the three types of order allowed in Pn
'
ma
'. In the Ca-rich corner of the system Ho
1-x
Ca
x
MnO
3
the title compound has a strong magnetoelastic distortion , the highest metallic conductivity and a ferromagnetic component F
y close to the maximum in the series. Among the areas ab, bc, ca calculated from the lattice constants only ca shows a strong magnetoelastic effect below T
N
= 106
K. The x-, y-, z-spin components depend differently on the temperature. This gives rise to spin rotation which is particularly strong close
to T
N. MnO
6
octahedra have short bond lengths with a temperature independent average . They are practically regular at room temperature and show a Jahn-Teller distortion of 3.5% in the magnetically ordered state.
Above T
N we find small polaron conductivity. The presence of the Jahn-Teller distortion due to the only small abundance (10%) of Mn
3+
in the t
2g
3
e
g configuration is attributed to delocalised e
g electrons. In the magnetically ordered state the averaged magnetic moment of Mn is reduced appreciably from the paramagnetic
value due to spin disorder.
Received 21 January 1999 相似文献
19.
J. Blasco J. García M.C. Sánchez J. Campo G. Subías J. Pérez-Cacho 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):469-479
Magnetic measurements have been carried out in different LaNi1-xMnxO
3 + δ
samples with 0.1 ⩽
x
⩽ 0.9. All these samples show two magnetic anomalies, one at relatively high temperature characteristic of a ferromagnetic ordering
and the other at low temperature, typical of magnetic relaxation phenomena. Neutron diffraction patterns indicate that long-range
ferromagnetic ordering is only achieved for x
≥ 0.5. Neutron patterns of LaNi0.5Mn0.5O
3 + δ
samples show an ordered arrangement of Ni and Mn atoms in the perovskite lattice. LaNi0.5Mn0.5O
3 + δ
is then, a double perovskite A2BB'O6 whereas Ni and Mn atoms are randomly distributed for the rest of the samples. X-ray magnetic circular dichroism experiments
confirm the presence of collinear ferromagnetism in LaNi0.5Mn0.5O
3 + δ
. The role of competitive magnetic interactions, structural disorder, magnetic anisotropy and magnetic disaccommodation is
also discussed
Received 19 July 2002 / Received in final form 23 October 2002 Published online 31 December 2002 相似文献
20.
S. Hébert A. Maignan R. Frésard M. Hervieu R. Retoux C. Martin B. Raveau 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):85-89
The doping of the manganese site by iridium (up to 15%) in the small A cation manganites Pr1-xCaxMnO3 ( 0.4 ?
x
? 0.8), has been investigated as a new method to suppress charge-ordering and induce CMR effects. Ir doping leads to ferromagnetism
and to insulator to metal transitions, with high transition temperatures reaching 180 K and CMR ratio in 7 T as large as 104. The efficiency with which iridium induces ferromagnetism and CMR is compared to previous results obtained with other substitutions
(Ru, Rh, Ni, Cr...). The ionic radius of the foreign cations and their mixed-valencies are found to be the main parameters
governing the ability to collapse the charge-ordered state.
Received 14 May 2001 and Received in final form 2 July 2001 相似文献