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11.
V. A. Ryzhov P. L. Molkanov A. V. Lazuta V. V. Runov V. P. Khavronin I. O. Troyanchuk 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1477-1480
We present the results from studying the magnetic properties (linear and nonlinear susceptibilities and the depolarization
of polarized neutrons) of Nd1 − x
Ba
x
MnO3 manganite, x = 0.3, with Curie temperature T
C ≈ 140 K and dielectric-to-metal transition temperature T
DM ≈ 129 K. Its critical behavior corresponds to that of an isotropic 3-D ferromagnet at temperatures above T*≈ 144 K, but a strong nonlinear response in weak magnetic fields and depolarization are observed at temperatures below T*. It is shown that this nontraditional behavior is related to the generation of ferromagnetic clusters in the paramagnetic
matrix that form a conducting percolative network at temperatures near T
DM. 相似文献
12.
I. O. Troyanchuk M. V. Bushinsky D. V. Karpinsky V. Sirenko V. Sikolenko V. Efimov 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,73(3):375-381
The Bi1−xAxFeO3−
δ (A = Sr, Pb)
systems have been studied using the X-ray, neutron powder
diffraction and magnetization measurements in a magnetic field up to
14 T. It was found that around x ∼ 0.06 the crystal symmetry
changes from a rhombohedral (space group R3c) to
pseudo-tetragonal. In the composition range
0.07 ≤ x ≤ 0.14 the phases with different symmetry of
the unit cell coexist independent of synthesis conditions. The
neutron powder diffraction shows that the iron ions have average
oxidation state close to 3+. The magnetic structure for
Bi0.5Sr0.5FeO3−
δ is found to be G-type
antiferromagnetic with magnetic moment of about
3.8 μB/Fe3+. The weak ferromagnetic state due to
magnetoelectric interactions was revealed in the lightly doped
rhombohedrally distorted compositions. No evidence for a spontaneous
magnetization was observed for the pseudo-tetragonal phases. These
compositions show irreversible nonlinear magnetization vs. field
behavior apparently due to small local deviations from the
collinearity of the magnetic moments. 相似文献
13.
S. V. Trukhanov I. O. Troyanchuk A. V. Trukhanov I. A. Bobrikov V. G. Simkin A. M. Balagurov 《JETP Letters》2006,84(5):254-257
The crystal structure of anion-deficient La0.70Sr0.30MnO3?δ manganites (δ = 0, 0.10, 0.15, and 0.20) has been studied by powder neutron diffraction at room temperature. The crystal structures of the stoichiometric La0.70Sr0.30MnO3 and anion-deficient La0.70Sr0.30MnO2.90 samples are satisfactorily described by the rhombohedral R $\bar 3$ c space group. The anion-deficient La0.70Sr0.30MnO2.85 sample separates into two perovskite phases with the R $\bar 3$ c and I4/mcm space groups. The crystal structure of La0.70Sr0.30MnO2.80 cannot be described by a single perovskite phase in the I4/mcm space group. It is found that the clustering of oxygen vacancies is the cause of structural phase separation at 293 K in anion-deficient La0.70Sr0.30MnO3?δ manganites. 相似文献
14.
I. O. Troyanchuk M. V. Bushinsky A. N. Chobot O. S. Mantytskaya N. V. Pushkarev R. Szymczak 《Journal of Experimental and Theoretical Physics》2008,107(2):245-250
Solid solutions of Bi1 ? x A x (Fe1 ? x/2Nb x/2)O3, where A = Ca, Ba, and Pb, are obtained and their crystal structure and magnetic properties are investigated. It is shown that for A = Ca and x ≈ 0.15, the symmetry of the unit cell changes from rhombohedral (space group R3c) to orthorhombic (Pbnm). The transformation leads to the emergence of spontaneous magnetization due to the Dzyaloshinskii-Moriya interaction. Solid solutions with A = Pb remain rhombohedral up to a concentration of x = 0.3. Spontaneous magnetization sharply increases in the compound with x ≈ 1 at low temperatures and is due to the formation of the spin-glass component. 相似文献
15.
H. Gamari-Seale I.O. Troyanchuk K.L. Stefanopoulos 《Physica B: Condensed Matter》2008,403(17):2924-2929
In this paper we report the study of the perovskites La0.7Ca0.3Mn0.5Co0.5O3 and La0.8Sr0.2Mn0.5Co0.5O3 by neutron powder diffraction at various temperatures and magnetization measurements in zero applied field and at low cooling regimes. The replacement of half Mn by Co in La0.7Ca0.3MnO3 and La0.8Sr0.2MnO3 destroys their long-range ferromagnetism exhibiting a cluster glass ferromagnetic order similar to the one observed in many cobaltites. 相似文献
16.
V. V. Sikolenko V. V. Efimov E. A. Levterova S. I. Tiutiunnikov I. O. Troyanchuk D. V. Karpinsky M. V. Bushinsky 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2020,14(1):17-23
We present the results of studying oxygen-deficient doped complex cobalt oxides by means of neutron diffraction and methods based on synchrotron radiation in the high energy range at low temperatures and a high external pressure. It is shown that the magnetic interactions in these compounds can be interpreted in terms of the model of superexchange between cobalt ions with different oxidation states. 相似文献
17.
I. O. Troyanchuk M. K. Karpuk O. S. Mantytskaya H. Szymczak 《Crystallography Reports》2004,49(4):626-630
Perovskites Bi0.5D0.5MnO3(D = Pb, Ba) were prepared under high pressure (4 GPa) at 1200–1300°C. According to the X-ray diffraction data, crystalline Bi0.5Pb0.5MnO3 has a tetragonal unit cell with the parameters a = 3.940 Å and c = 3.800 Å, whereas Bi0.5Ba0.5MnO3 crystals are cubic with a = 3.940 Å. It is concluded from magnetic studies that lead-containing manganite is an antiferromagnet with TN = 120 K, whereas Bi0.5Ba0.5MnO3 is a spin glass with spin-freezing temperature T f = 38 K. Both compounds are decomposed upon heating in air at temperatures above 500°C. With the use of synthesis in air, Bi0.5Ca0.5 ? xD x MnO3 solid solutions with x as high as 0.25 were obtained. 相似文献
18.
D. V. Karpinsky I. O. Troyanchuk V. M. Dobryansky R. Szymczak M. Tovar 《Crystallography Reports》2006,51(4):596-600
The magnetic and crystal structures of the LaCo0.5Fe0.5O3 perovskite are investigated. It is established that the unit cell of this compound at room temperature is characterized by rhombohedral distortions. As the temperature decreases, the compound undergoes a structural phase transition from the rhombohedral phase to the orthorhombic phase in the temperature range 200–300 K. The LaCo0.5Fe0.5O3 perovskite has an antiferromagnetic structure with the G z spatial orientation of the antiferromagnetic vector. The magnetic properties of the LaCo0.5Fe0.5O3 perovskite are interpreted within a model according to which the ground state of Co3+ ions is a low-spin state and the existence of the weak ferromagnetic component is associated with the exchange interactions between the Fe3+ ions. 相似文献
19.
I.O. Troyanchuk N.V. Tereshko A.N. Chobot M.V. Bushinsky K. Brner 《Physica B: Condensed Matter》2009,404(21):4185-4189
The Bi1−xAxFe1−xTixO3 (A—Ca, Sr, Pb, Ba) and BiFe1−xTixO3+δ systems have been studied using X-ray, neutron powder diffraction and magnetization measurements in a magnetic field up to 14 T. It was found that all Bi1−xAxFe1−xTixO3 solid solutions are rhombohedral up to x=0.3. In the case of BiFe1−xTixO3+δ the rhombohedral distortion preserved up to x=0.11. A homogeneous weakly ferromagnetic state was found for Bi1−xCaxFe1−xTixO3 (0.15≤x≤0.25) and BiFe1−xTixO3+δ (0.06≤x≤0.11), probably due to magnetoelectric interactions, whereas Bi1−xAxFe1−xTixO3 (A—Sr, Pb, Ba) compounds above doping level x>0.1 seem to be collinear antiferromagnets. 相似文献
20.
The crystal structure and magnetic properties of the Bi1 ? x Ca x Fe1 ? x/2Nb x/2O3 system were studied. It is shown that, at x ≤ 0.15, the unit-cell symmetry of solid solutions is rhombohedral (space group R3c). Solid solutions with x ≥ 0.3 have an orthorhombic unit cell (space group Pbnm). The rhombohedral compositions are antiferromagnetic, while the orthorhombic compositions exhibit a small spontaneous magnetization due to Dzyaloshinski?-Moriya interaction. In CaFe0.5Nb0.5O3, the Fe3+ and Nb5+ ions are partially ordered and the unit cell is monoclinic (space group P21/n). In the concentration range 0.15 < x < 0.30, a two-phase state (R3c + Pbnm) is revealed. 相似文献