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51.
Troyanchuk I. O. Bushinsky M. V. Dobryanskii V. M. Pushkarev N. V. 《JETP Letters》2012,94(12):849-852
JETP Letters - In layered Sr3YCo4O10.5 + δ-type cobaltites with different oxygen contents, we have observed a first order magnetic phase transition from the high-temperature... 相似文献
52.
A. M. Balagurov I. A. Bobrikov D. V. Karpinsky I. O. Troyanchuk V. Yu. Pomjakushin D. V. Sheptyakov 《JETP Letters》2008,88(8):531-536
The crystal and magnetic structures of the Pr0.5Sr0.5CoO3 metallic ferromagnet have been studied using neutron diffraction and synchrotron radiation. Successive structural transitions with the reduction of the crystal symmetry from cubic (space group Pm3m) to rhombohedral (\(R\bar 3c\), ~800 K), orthorhombic (Imma, ~300 K) and, then, to triclinic at ~120 K are detected during cooling from 1120 K. The transition from the orthorhombic system to a phase with a lower symmetry is characterized by a sharp change in the anisotropy of the unit cell, which indicates the partial ordering of the e g orbitals of cobalt. The accompanying change in the interatomic distances and valence angles give rise to an anomaly in the temperature dependence of the magnetic susceptibility at T ≈ 120 K. The ordered magnetic moment μCo ≈ 2μB corresponds to the assumption of the intermediate spin state of Co3+ ions and the mixture of low- and intermediate-spin states of Co4+ ions. 相似文献
53.
I. O. Troyanchuk D. V. Karpinsky M. V. Bushinskii O. Prokhnenko M. Kopcevicz R. Szymczak J. Pietosa 《Journal of Experimental and Theoretical Physics》2008,107(1):83-89
Systems of solid solutions Bi1 − x
Ca
x
FeO3 (I) and Bi1 − x
CaxFeO1 − x
Ti
x
O3 (II) have been obtained and their properties have been studied using neutronography and M?ssbauer spectroscopy; magnetization
and permittivity have been measured. It is shown that an increase in the concentration of calcium ions in system I for x > 0.2 changes rhombohedral distortions of a unit cell (space group R3c) to tetragonal distortions (space group I4/mcm), while rhombohedral distortions in system II for x > 0.2 are replaced by orthorhombic distortions (space group Pnma). Analysis of the crystal structure has revealed strong anisotropy in vibrations of Bi and O ions in system I compounds.
Systems I and II are characterized by G-type antiferromagnetic ordering of magnetic moments. In system II, spontaneous magnetization
associated with the Dzyaloshinskii-Moriya interaction has been detected. According to M?ssbauer spectroscopy data, iron ions
in compounds I and II are in the trivalent state and charge compensation occurs due to the formation of oxygen vacancies.
The permittivity increases with the calcium concentration.
Original Russian Text ? I.O. Troyanchuk, D.V. Karpinsky, M.V. Bushinskii, O. Prokhnenko, M. Kopcevicz, R. Szymczak, J. Pietosa,
2008, published in Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2008, Vol. 134, No. 1, pp. 105–112. 相似文献
54.
I. O. Troyanchuk V. A. Khomchenko H. Szymczak M. Baran 《Journal of Experimental and Theoretical Physics》2003,97(6):1231-1239
The magnetic properties of manganites of the Nd1?xCaxMnO3 system with x≤0.15 have been studied. It is shown that, in the 0.06≤x≤0.1 interval, the results can be interpreted using a model according to which the concentrational transition from a weakly ferromagnetic (WFM) state (x=0) to a ferromagnetic (FM) state (x>0.15) proceeds via a mixture of the exchange-coupled FM and WFM phases. In the vicinity of T=9 K, samples with 0.06≤x≤0.1 exhibit a spontaneous magnetic phase transition involving reorientation of the magnetization vectors of the WFM and the exchange-coupled FM phases. In the temperature interval between 5 and 20 K, a sample with the composition Nd0.92Ca0.08MnO2.98 exhibits metamagnetic behavior. Magnetic phase diagrams in the H?T and T?x coordinates are presented. The appearance of the spin-reorientation transitions is explained in terms of the magnetic analog of the Jahn-Teller effect with allowance for the fact that, according to the neutron diffraction data, the magnetic moments of neodymium ions in the FM phase are parallel to the magnetic moments of manganese ions. 相似文献
55.
I.O. Troyanchuk M.V. Bushinsky H. Szymczak M. Baran K. Bärner 《Journal of magnetism and magnetic materials》2007
Powder neutron diffraction and magnetic studies have been performed for NdMn0.5Fe0.5O3 and NdMn0.5Cr0.5O3 manganites. In NdMn0.5Cr0.5O3, magnetic structure has been revealed consisting of ferromagnetic and G-type antiferromagnetic components as result of a 3d-ions magnetic moments ordering. Magnetic moments of Nd-ions are parallel to the ferromagnetic component. In NdMn0.5Fe0.5O3 only the antiferromagnetic G-type structure has been found whereas Nd-sublattice was not ordered. In the both compounds, magnetic moments of 3d-ions are significantly less than one can expect, what is interpreted in terms of intrinsic chemical inhomogeneity. Magnetic phase diagrams have been constructed for the Nd(Mn1−xMx)O3 (M=Fe, Cr) systems, interpreted assuming superexchange interactions Mn3+–O–Cr3+ to be positive, Mn3+–O–Fe3+ negative and taking into account a disordered arrangement of Mn and Cr ions in the crystal structure sublattice as well as interplay between Jahn–Teller effect and superexchange interactions. 相似文献
56.
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
57.
S. V. Trukhanov I. O. Troyanchuk I. A. Bobrikov V. G. Simkin A. M. Balagurov 《Crystallography Reports》2007,52(5):805-810
The crystal structure of the anion-deficient manganites La0.7Sr0.3MnO3 ? δ (δ = 0, 0.10, 0.15, 0.20) is investigated using high-resolution neutron diffraction. At room temperature, the crystal structure of the stoichiometric manganite La0.7Sr0.3MnO3 and the anion-deficient manganite La0.7Sr0.3MnO2.9 is satisfactorily described in rhombohedral space group R \(\bar 3\) c. The anion-deficient manganite La0.7Sr0.3MnO2.85 is characterized by two perovskite phases with space groups R \(\bar 3\) c and 14/mcm. The crystal structure of the La0.7Sr0.3MnO2.8 manganite corresponds to the structure of a perovskite phase with space group I4/mcm. It is established that the phase separation in the crystal structure of the La0.7Sr0.3MnO3 ? δ manganites at a temperature of 293 K is associated with a nonuniform distribution of oxygen vacancies. 相似文献
58.
I. O. Troyanchuk M. V. Bushinsky V. M. Dobryanskii N. V. Pushkarev 《JETP Letters》2011,94(12):849-852
In layered Sr3YCo4O10.5 + δ-type cobaltites with different oxygen contents, we have observed a first order magnetic phase transition from the high-temperature
“ferromagnetic” state to the low-temperature antiferromagnetic state. The transition can be induced by an applied magnetic
field. It is accompanied by a significant hysteresis in the magnetic field (∼10 T) and temperature (∼10 K). A decrease and
an increase in the yttrium content lead to a purely “ferromagnetic” and antiferromagnetic behavior, respectively. 相似文献
59.
A. M. Balagurov I. A. Bobrikov V. Yu. Pomjakushin E. V. Pomjakushina D. V. Sheptyakov I. O. Troyanchuk 《JETP Letters》2011,93(5):263-268
The magnetic and crystal structures of the Pr0.5Sr0.5CoO3 metallic ferromagnet have been studied by the neutron diffraction technique. It is demonstrated that below 150 K, the compound
is mesoscopically separated into two crystalline phases with different spatial symmetries and with different directions of
the magnetic anisotropy. The phase separation exists down to 1.5 K, and at temperatures below 90 K, the low-symmetry phase
occupies about 80% of the sample volume. The main structural difference between the phases is the configuration of oxygen
atoms around praseodymium and, to a certain extent, around cobalt. The ferromagnetic structure with the magnetic moment lying
in the basal plane of the structure (μCo ≈ 1.7 μ
B
at 1.5 K) arises at 234 K, whereas the component directed along the long axis of the unit cell appears at 130 K. The formation
of the new structural phase and change in the orientation of the magnetic moment give rise to the anomalies of the physical
and magnetic characteristics of this compound observed earlier at temperatures about 120 K. 相似文献
60.
In this work, X-ray diffraction data taken on Bi1−xLaxFeO3 solid solutions are used to verify the following structural phase transitions: “polar rhombohedral-antipolar orthorhombic” at x≈0.16 and “commensurate-incommensurate” within the orthorhombic phase at x≈0.18. In contrast, in the Bi1−xPrxFeO3 series, the polar rhombohedral phase transforms into an antipolar orthorhombic one at x≥0.13. The polar rhombohedral phase near the morphotropic phase boundary exhibits an isothermal transformation into an antipolar orthorhombic phase, though the transformation occurs much faster in the case of La-doped compounds. The incommensurate structural phase was not detected in Bi1−xPrxFeO3 solid solutions. The ternary structural phase diagram is constructed for (Bi,La,Pr)FeO3 systems. In addition, the polar rhombohedral phase exhibits a magnetic field-induced transition from the modulated antiferromagnetic state into a homogeneous weak ferromagnetic state whereas the antipolar phase is a weak ferromagnetic state in the absence of an external field. 相似文献