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1.
G. A. Petrakovskii L. N. Bezmaternykh I. A. Gudim D. Sheptyakov O. A. Bayukov A. M. Vorotynov D. A. Velikanov A. F. Bovina 《Physics of the Solid State》2005,47(11):2114-2118
The magnetic susceptibility and specific heat of single crystals of the Ba2Fe2GeO7 barium ferrigermanate are investigated. It is revealed that the temperature dependence of the magnetic susceptibility exhibits a kink at a temperature T = 8.5 K. The number of nonequivalent positions of Fe3+ ions and their occupancies are determined using Mössbauer spectroscopy. It is shown that the Fe3+ ions located in tetrahedral positions T2 are ordered incompletely, which is inconsistent with the results obtained previously. An assumption is made regarding the possible ground magnetic state of the Ba2Fe2GeO7 compound. 相似文献
2.
We report transport, magnetic and thermodynamic properties of the
skutterudite compound LaFe4Sb12. The basic features are a large
magnetic susceptibility χ(T), and large electronic coefficient
γ of the heat capacity. In particular, a T1.35, T1.7, and
T-2/3 temperature dependence of the magnetic susceptibility χ(T),
resistivity ρ(T), and Grüneisen parameter Γ(T), respectively, is found at low temperature. An overall understanding of these physical properties is achieved, assuming that
LaFe4Sb12 is a non-Fermi liquid system close to a ferromagnetic quantum critical point, with a spin fluctuation temperature Tsf=50±15 K. 相似文献
3.
Y. Xiao Y. Su C. M. N. Kumar C. Ritter R. Mittal S. Price J. Perßon Th. Brückel 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,82(2):113-121
The physical and structural properties of Fe1.11Te and
Fe1.11Te0.5Se0.5 have been investigated by means of
X-ray and neutron diffraction as well as physical property
measurements. For the Fe1.11Te compound, the structure
distortion from a tetragonal to monoclinic phase takes place at 64 K
accompanied with the onset of antiferromagnetic order upon cooling.
The magnetic structure of the monoclinic phase was confirmed to be
of antiferromagnetic configuration with a propagation vector
k = (1/2, 0, 1/2) based on Rietveld refinement of neutron
powder diffraction data. The structural/magnetic transitions are
also clearly visible in magnetic, electronic and thermodynamic
measurements. For superconducting Fe1.11Te0.5Se0.5
compound, the superconducting transition with T
c
= 13.4 K
is observed in the resistivity and ac susceptibility measurements.
The upper critical field H
c2 is obtained by measuring
the resistivity under different magnetic fields. The Kim’s critical
state model is adopted to analyze the temperature dependence of the
ac susceptibility and the intergranular critical current density is
calculated as a function of both field amplitude and temperature.
Neutron diffraction results show that
Fe1.11Te0.5Se0.5 crystalizes in tetragonal structure
at 300 K as in the parent compound Fe1.11Te and no structural
distortion is detected upon cooling to 2 K. However an anisotropic
thermal expansion anomaly is observed around 100 K. 相似文献
4.
V. G. Kytin B. M. Bulychev A. V. Krechetov E. A. Konstantinova V. A. Kulbachinskiĭ R. A. Lunin 《Journal of Experimental and Theoretical Physics》2007,105(1):250-252
A series of new heterofullerides with compositions Rb2MC60, K2MC60, and KM2C60 (M = Mg, Be) have been synthesized. Measurements of the temperature dependences of the magnetic susceptibility in the temperature interval from 4.2 to 300 K reveal a superconducting transition in heterofullerides K2MgC60, KMg2C60, K2BeC60, and Rb2BeC60 at temperatures T c = 13–22 K. The electron states with uncompensated spin are studied by the electron paramagnetic resonance technique. The contributions of conduction electrons and localized electrons to the paramagnetic susceptibility are extracted. 相似文献
5.
V. E. Arkhipov A. E. Kar’kin Ya. M. Mukovskii R. V. Pomortsev 《Physics of the Solid State》2005,47(9):1697-1700
The temperature dependences of the electrical resistivity ρ(T) and the ac magnetic susceptibility χ(T, H = 0) are thoroughly investigated for a perovskite-like lanthanum manganite, namely, La0.85Sr0.15MnO3, which is preliminarily exposed to neutron irradiation with a fluence F = 2 × 1019 cm?2 and then annealed at different temperatures ranging from 200 to 1000°C. The results of the electrical resistance measurements demonstrate that neutron irradiation of the samples leads to the disappearance of the low-temperature insulating phase. As the annealing temperature increases, the insulating phase is not restored and the manganite undergoes a transformation into a metallic phase. Analysis of the magnetic properties shows that, under irradiation, the ferromagnet-paramagnet phase transition temperature TC decreases and the magnetic susceptibility is reduced significantly. With an increase in the annealing temperature, the phase transition temperature TC and magnetic susceptibility χ(T, H = 0) increase and gradually approach values close to those for an unirradiated sample. This striking difference in the behavior of the electrical and magnetic properties of the radiation-disordered La0.85Sr0.15MnO3 manganite is explained qualitatively. 相似文献
6.
E. Govea-Alcaide I. García-Fornaris P. Muné R. F. Jardim 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):373-378
Measurements of the electrical resistivity as a function
of temperature, ρ(T), for different values of applied
magnetic field, Ba (0 ≤ Ba ≤ 50 mT), were performed in
polycrystalline samples of Bi1.65Pb0.35Sr2Ca2
Cu3O10+δ subjected to different uniaxial compacting
pressure (UCP). We have found appreciable differences in the grain
orientation between samples by using X-ray diffractometry. From
the X-ray diffraction patterns performed, in powder and pellet
samples, we have estimated the Lotgering factor along the (00l)
direction, F(00l). The results indicate that F(00l)
increases ~23% with increasing UCP suggesting that grains
of these samples are preferentially aligned along the c-axis,
which is parallel to the compacting direction. The resistive
transition of the samples have been interpreted in terms of the
thermally activated flux-creep model. In addition, the effective
intergranular pinning energy, U0, have been determined for
different applied magnetic field. The magnetic field dependence of
U0, for Ba > 8 mT, was found to follow a H- α
dependence with α = 0.5 for all samples. The analysis of the
experimental data strongly suggested that increasing UCP results
in appreciable changes in both the grain alignment and the grain
connectivity of the samples. We have successfully interpreted the
data by considering the existence of three different
superconducting levels within the samples: the superconducting
grains, the weak-links, and the superconducting clusters. 相似文献
7.
We investigated the stability of magnetic moments in
Al69.8Pd12.1Mn18.1. This alloy exists in both, the
icosahedral (i) and the decagonal (d) quasicrystalline form.
The transition from the i- to the d-phase is achieved by a
simple heat treatment. We present the results of measurements of
the 27Al NMR-response, the dc magnetic susceptibility, and
the low-temperature specific heat of both phases. In the
icosahedral compound, the majority of the Mn ions carries a
magnetic moment. Their number is reduced by approximately a factor
of two by transforming the alloy to its decagonal variety. For
both compounds, we have indications for two different local
environments of the Al nuclei. The first reflects a low density of
states of conduction electrons and a weak coupling of the Al
nuclei to the Mn-moments. The second type of environment implies a
large d-electron density of states at the Fermi level and a
strong coupling to the magnetic Mn moments. Spin-glass freezing
transitions are observed at Tdecaf=12 K for the
decagonal, and Ticof=19 K for the icosahedral phase. 相似文献
8.
B. Pedrini S. Wessel J. L. Gavilano H. R. Ott S. M. Kazakov J. Karpinski 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):219-228
We report results of susceptibility χ and 7Li NMR measurements on LiVSi2O6. The temperature dependence of the magnetic susceptibility χ(T) exhibits a broad maximum, typical for low-dimensional magnetic
systems. Quantitatively it is in agreement with the expectation for an S=1 spin chain, represented by the structural arrangement
of V ions.
The NMR results indicate antiferromagnetic ordering below TN=24 K. The intra- and interchain coupling J and Jp for LiVSi2O6, and also for its sister compounds LiVGe2O6, NaVSi2O6 and NaVGe2O6, are obtained via a modified random phase approximation which takes into account results of quantum Monte Carlo calculations.
While Jp is almost constant across the series, J varies by a factor of 5, decreasing with increasing lattice constant along the chain
direction. The comparison between experimental and theoretical susceptibility data suggests the presence of an easy-axis magnetic
anisotropy, which explains the formation of an energy gap in the magnetic excitation spectrum below TN, indicated by the variation of the NMR spin-lattice relaxation rate at T≪TN. 相似文献
9.
G. Kh. Panova A. A. Shikov N. A. Chernoplekov A. A. Zhokhov A. N. Maljuk C. T. Lin 《Physics of the Solid State》2003,45(12):2237-2241
The anisotropy in the superconducting properties of single-crystal Nd1.85Ce0.15CuO4 was studied from measurements of the heat capacity within the temperature interval 2–40 K in zero magnetic field and in a magnetic field of 8 T. We report on the first observation of heat capacity jumps occurring at the superconducting transition for various magnetic field orientations with respect to the crystallographic axes and on a strong anisotropy of the magnetic contribution to heat capacity in magnetic fields oriented in the a-b plane and perpendicular to it. These measurements yielded the anisotropy in the electronic heat capacity coefficient γn(H) and in the superconducting transition temperature Tc(H). The angular dependence of the Sommerfeld coefficient γn in the a-b plane observed in a magnetic field of 8 T exhibits four-lobe symmetry and zero gap direction of the order parameter. A comparison of the results obtained on the Nd1.85Ce0.15CuO4 single crystal with the data available for La1.85Sr0.15CuO4 permits one to conclude that the mechanisms of superconductivity in the electron-and hole-doped superconductors are similar. 相似文献
10.
Metastable superconductivity of the Al/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> interface
Superconductivity in the interface region between metallic Al and its oxide, Al2O3, has been detected at about 45 K in the measured dynamic magnetic susceptibility. 相似文献
11.
Yu. A. Aleshchenko A. V. Muratov V. M. Pudalov E. S. Zhukova B. P. Gorshunov F. Kurth K. Iida 《JETP Letters》2012,94(9):719-722
The results of infrared reflectivity measurements for the iron-based high-temperature superconductor Ba(Fe0.9Co0.1)2As2 are reported. The reflectivity is found to be close to unity at frequencies ω lower than 2Δ/h (2Δ is the superconducting gap and h is Planck’s constant). This is evidence for the s
+/− or s
+/+ symmetry of the superconducting order parameter in the studied compound. The infrared reflectivity spectra of Ba(Fe0.9Co0.1)2As2 manifest opening of several superconducting gaps at temperatures lower than critical T
c
. 相似文献
12.
The momentum-transfer dependence of the magnetic form factor associated with the quasielastic spectral component in the dynamic magnetic response of intermediate valence SmB6 has been measured using inelastic neutron scattering on a double-isotope (154Sm, 11B) single crystal. The experimental dependence differs qualitatively from those obtained earlier for the inelastic signals, as well as from the field-induced magnetic form factor of SmB6 obtained by polarized neutron diffraction. This observation is interpreted by specifically considering the Curie-type contributions to the dynamic susceptibility, which arise from the mixing of 4 f5 and 4 f6J-multiplets into the intermediate valence state wavefunction. 相似文献
13.
A powder X-ray diffraction study, combined with magnetic susceptibility and electric
transport measurements, was performed on a series of LnCoO3 perovskites (Ln = Y, Dy, Gd, Sm, Nd,
Pr and La) over a temperature range 100–1000 K. A non-standard temperature dependence of the
observed thermal expansion was modelled as a sum of three contributions: (1) weighted sum of
lattice expansions of the cobaltite in the diamagnetic low spin state and in the intermediate
(IS) or high (HS) spin state. (2) An anomalous expansion due to the increasing population of
excited (IS or HS) states of Co3+ ions over the course of the diamagnetic-paramagnetic
transition. (3) An anomalous expansion due to excitations of Co3+ ions to another
paramagnetic state accompanied by an insulator-metal transition.
The anomalous expansion is governed by parameters that are found to vary linearly with the Ln
ionic radius. In the case of the first magnetic transition it is the energy splitting E
between the ground low spin state and the excited state, presumably the intermediate spin state.
The energy splitting E, determined by a fit to magnetic susceptibility, decreases with
temperature. The values of E determined for LaCoO3 and YCoO3 at T=0 K are 164 K and
2875 K respectively, which fall to zero at T=230 K for LaCoO3 and 860 K for YCoO3. The second
anomalous expansion connected with a simultaneous magnetic and insulator-metal transition is
characterized by its center at T=535 K for LaCoO3 and 800 K for YCoO3. The change of the unit
cell volume during each transition is independent of the Ln cation and is about 1% in both
cases. 相似文献
14.
V. P. Dyakonov R. Szymczak A. D. Prokhorov E. Zubov A. A. Prokhorov G. Petrakovskii L. Bezmaternikh M. Berkowski V. Varyukhin H. Szymczak 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):291-298
Magnetic and electron paramagnetic resonance (EPR) properties of
EuFe3(BO3)4 single crystals have been studied over the
temperature range of 300–4.2 K and in a magnetic field up to 5 T. The
temperature, field and orientation dependences of susceptibility,
magnetization and EPR spectra are presented. An antiferromagnetic ordering
of the Fe subsystem occurs at about 37 K. The easy direction of
magnetization perpendicular to the c axis is determined by magnetic
measurements. Below 10 K, we observe an increase of susceptibility connected
with the polarization of the Eu sublattice by an effective exchange field of
the ordered Fe magnetic subsystem. In a magnetic field perpendicular to the
c axis, we have observed an increase of magnetization at T < 10 K in the
applied magnetic field, which can be attributed to the appearance of the
magnetic moment induced by the magnetic field applied in the basal plane.
According to EPR measurements, the distance between the maximum and minimum
of derivative of absorption line of the Lorentz type is equal to 319 Gs. The
anisotropy of g-factor and linewidth is due to the influence of crystalline
field of trigonal symmetry. The peculiarities of temperature dependence of
both intensity and linewidth are caused by the influence of excited states
of europium ion (Eu3+). It is supposed that the difference between the
g-factors from EPR and the magnetic measurements is caused by exchange
interaction between rare earth and Fe subsystems via anomalous Zeeman
effect. 相似文献
15.
E. A. Popova N. Tristan C. Hess R. Klingeler B. Büchner L. N. Bezmaternykh V. L. Temerov A. N. Vasil’ev 《Journal of Experimental and Theoretical Physics》2007,105(1):105-107
The neodymium ferroborate NdFe3(BO3)4 undergoes an antiferromagnetic transition at T N = 30 K, which manifests itself as a λ-type anomaly in the temperature dependence of the specific heat C and as inflection points in the temperature dependences of the magnetic susceptibility χ measured at various directions of an applied magnetic field with respect to the crystallographic axes of the sample. Magnetic ordering occurs only in the subsystem of Fe3+ ions, whereas the subsystem of Nd3+ ions remains polarized by the magnetic field of the iron subsystem. A change in the population of the levels of the ground Kramers doublet of neodymium ions manifests itself as Schottky-type anomalies in the C(T) and χ(T) dependences at low temperatures. At low temperatures, the magnetic properties of single-crystal NdFe3(BO3)4 are substantially anisotropic, which is determined by the anisotropic contribution of the rare-earth subsystem to the magnetization. The experimental data obtained are used to propose a model for the magnetic structure of NdFe3(BO3)4. 相似文献
16.
A. A. Voronkov B. P. Gorshunov V. S. Nozdrin E. S. Zhukova T. Matsuoka K. Tanaka S. Miyasaka S. Tajima M. Dressel 《JETP Letters》2012,94(9):708-713
The spectra of the conductivity and dielectric constant of La1.87Sr0.13CuO4 cuprate have been directly measured in the frequency range of 0.3 to 1.2 THz (10–40 cm−1) and the temperature range of 5 to 300 K in the E | c polarization (the electric field vector of radiation is perpendicular to the copper-oxygen planes). Excitation has been observed
in the superconducting phase, and its nature has been attributed to the transverse optical excitation of the condensate of
Cooper pairs, which appears because Josephson junctions between CuO planes are modulated due to in-plane magnetic and charge
stripes. Additional quasiparticle absorption of unknown origin has been detected at frequencies below ≈15 cm−1 at liquid helium temperatures. 相似文献
17.
T. V. Drokina G. A. Petrakovskii L. Keller J. Schefer A. D. Balaev A. V. Kartashev D. A. Ivanov 《Journal of Experimental and Theoretical Physics》2011,112(1):121-126
The magnetic structure of the NaFeGe2O6 monoclinic compound has been experimentally investigated using the elastic scattering of neutrons. At a temperature of 1.6
K, an incommensurate magnetic structure has been observed in the form of an antiferromagnetic helix formed by a pairs of the
spins of the Fe3+ ions with helical modulation in the ac plane of the crystal lattice. The wave vector of the magnetic structure has been determined and its temperature behavior
has been studied. The analysis of the temperature dependences of the specific heat and susceptibility, as well as the isotherms
of the field dependence of the magnetization, has revealed the existence of not only the order-disorder magnetic phase transition
at the point T
N = 13 K, but also an additional magnetic phase transition at the point T
c = 11.5 K, which is assumingly an orientation phase transition. 相似文献
18.
L. G. Mamsurova K. S. Pigalskiy N. G. Trusevich N. B. Butko A. A. Vishnev 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(4):547-549
The characteristics determining different contributions to the magnetic susceptibility at T > T C (Pauli susceptibility, coherence length at T = 0, and Curie constant) as functions of the degree of structural disorder have been analyzed for high-temperature superconducting YBa2Cu3O y samples ( y ≈ 6.92, T C ≈ 92 K) with micrometer and submicron average grain sizes D av. It is shown that the decrease in these characteristics, which is observed in fine-grained samples with a decrease in D av, occurs in various ways, depending on the number and type of oxygen vacancy ordering in chain planes. 相似文献
19.
N. B. Ivanova N. V. Kazak C. R. Michel A. D. Balaev S. G. Ovchinnikov 《Physics of the Solid State》2007,49(11):2126-2131
The temperature and magnetic field dependences of the static magnetization of the polycrystalline rare-earth cobaltites GdCoO3 and SmCoO3 have been measured. It is shown that, below room temperature, the magnetization of both compounds derives primarily from the rare-earth ion paramagnetism. The GdCoO3 and SmCoO3 compounds have been found to differ substantially in magnetic behavior, which can be traced to differences in their electronic shell structures. The magnetic behavior of GdCoO3 is close to that of an array of free Gd3+ ions, whereas in SmCoO3 the deviation from the free-ion properties is very large because of the Sm3+ ground state being crystal-field split. Van Vleck magnetic susceptibility measurements of SmCoO3 suggest that the splitting is ~10 K. 相似文献
20.
Magnetization M(H,T) in magnetic fields H up to 90 kOe and at temperatures 2 K ≤ T < T c (where Tc is the superconducting transition temperature), along with magnetic susceptibility χ(T) in the normal state T c < T < 400 K for optimally oxygen-doped samples of YBa2Cu3O6.92 with varying degrees of defects in the crystal structure, are studied to determine the influence of structural inhomogeneity on the electron systems characteristics of cuprate superconductors. It is shown that the existence of structural inhomogeneity of samples leads to the manifestation of peculiarities appropriate to pseudogap regime in their properties. 相似文献