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1.
A. A. Demidov I. A. Gudim E. V. Eremin 《Journal of Experimental and Theoretical Physics》2012,114(2):259-272
The magnetic properties of ferroborate single crystals with substituted compositions Nd1 − x
Dy
x
Fe3(BO3)4 (x = 0.15, 0.25) with competing exchange Nd-Fe and Dy-Fe interactions are investigated. For each composition, we observed a
spontaneous spin-reorientation transition from the easy-axis to the easy-plane state and step anomalies on the magnetization
curves for the spin-flop transition induced by a magnetic field B | c. The measured parameters and effects are interpreted using a unified theoretical approach based on the molecular field approximation
and on calculations performed in the crystal-field model for the rare-earth ion. The experimental temperature dependences
of the initial magnetic susceptibility from T = 2 K to T = 300 K, anomalies on the magnetization curves for B | c in fields up to 1.8 T, and their evolution with temperature, as well as temperature and field dependences of magnetization
in fields up to 9 T are described. In the interpretation of experimental data, the crystal-field parameters in trigonal symmetry
for the rare-earth subsystem are determined, as well as the parameters of Nd-Fe and Dy-Fe exchange interactions. 相似文献
2.
G. I. Harus A. N. Ignatenkov N. K. Lerinman A. I. Ponomarev L. D. Sabirzyanova N. G. Shelushinina N. A. Babushkina L. M. Belova 《JETP Letters》1996,64(6):444-449
The temperature and magnetic-field dependences of the resistivity ρ and Hall effect R(j‖ab, B‖c) in a Nd1.82Ce0.18CuO4−δ
single crystal film (T
c
=6 K) is investigated at temperatures 1.4≤T≤20 K and magnetic fields 0≤B≤5.5 T. At the lowest temperature T=1.4 K the resistive state (exhibiting resistivity and the Hall effect) arises in a magnetic field B=0.5 T. A transition to the normal state is completed at B
c
2≃3 T, where the Hall coefficient becomes nearly constant. The negative magnetoresistance due to the weak-localization effect
in the normal state is observed for B>3 T. The nonmonotonic behavior and the inversion of the sign of R(B) in the mixed state are explained in a reasonable way by the flux-flow model with the effect of pinning taken into account.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 6, 407–411 (25 September 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
3.
D. Herlach G. Majer J. Major J. Rosenkranz M. Schmolz W. Schwarz A. Seeger W. Templ E. H. Brandt U. Essmann K. Fürderer M. Gladisch 《Hyperfine Interactions》1991,63(1-4):41-48
The spin precession of positive muons in ultra-pure Nb single crystals of high perfection, cooled down in transverse magnetic
fields 0.68B
c2≤B
appl≤0.84B
c2 (B
c2=upper critical field) from temperatures well above the superconducting transition temperatureT
c=9.25 K, has been investigated in the temperature range 2.6 K≤T≤8.0 K. The experiments confirm the periodic fieldB(r) of triangular flux-line lattices as calculated from numerical solutions of the microscopic BCS-Gor'kov theory. The observed
broadening of the van Hove singularities in the field distribution is discussed in terms of the combined effects of muon diffusion
and random perturbations of the flux-line lattice. 相似文献
4.
V. E. Arkhipov V. E. Startsev V. P. Dyakina J. Klamut Ya. M. Mukovskii A. Czopnik 《JETP Letters》1998,68(1):42-46
Magnetization measurements were performed on a lanthanum manganite La0.9Sr0.1MnO3 single crystal in the temperature interval 4.2–300 K and magnetic field interval 50 Oe-55 kOe in two sample cooling regimes:
1) cooling down to 4.2 K in a high (55 kOe) magnetic field, and 2) cooling in a “zero” field. It is shown that the temperature
dependences of the magnetization M(T) are substantially different in these regimes. Pronounced anomalies of M(T) were observed at temperatures T*=103 K and T
c
=145 K. The first anomaly is attributed to a structural transition, while the second one corresponds to a ferromagnet-paramagnet
phase transition. The magnetization of a La0.9Sr0.1MnO3 single crystal in the cooling regimes studied shows typical “spin-glass” behavior.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 39–43 (10 July 1998) 相似文献
5.
V. P. D’yakonov V. I. Markovich V. L. Kovarskii A. V. Markovich M. Borowiec A. Jedrzejczak H. Szymczak 《Physics of the Solid State》1998,40(4):691-698
The low-temperature thermal and magnetic-resonance properties of a monoclinic KDy(WO4)2 single crystal are investigated. It is established that a structural phase transition takes place at T
c=6.38 K. The field dependence of the critical temperature is determined for a magnetic field oriented along the crystallographic
a and c axes. The initial part of the H-T phase diagram is plotted for H∥a. The prominent features of the structural phase transition are typical of a second-order Jahn-Teller transition, which is
not accompanied by any change in the symmetry of the crystal lattice in the low-temperature phase. The behavior of C(T) in a magnetic field shows that the transition goes to an antiferrodistortion phase. An anomalous increase in the relaxation
time (by almost an order of magnitude) following a thermal pulse is observed at T>T
c(H), owing to the structural instability of the lattice. A theoretical model is proposed for the structural phase transition
in a magnetic field, and the magnetic-field dependence of T
c is investigated for various directions of the field.
Fiz. Tverd. Tela (St. Petersburg) 40, 750–758 (April 1998) 相似文献
6.
Evidence that pinning on linear or planar defects dominates the vortex dynamics in YBa2Cu3O7−x (YBCO) films is provided by complex impedance measurements at temperature 8 K<T<T
c
and magnetic field 0<B<6 T. Below the vortex lattice melting transition Bg(T) but above a threshold field Bp≈8(1-T/T
c
) T, the inductance of vortices increases as B2, much less rapidly than predicted for collective pinning of vortices by point defects. Above the vortex melting line, critical
scaling persists over the region Bg(T<B<B*(T) where the vortex correlation length ξ exceeds a characteristic length scale ξ*≡ξ(B=B*)≈450?. The value of ξ* is not sensitive to Al-doping in the Cu sites in the lattice and is close to the size of twin domains in the film. The nature
of the observed crossovers is discussed in terms of available theoretical models for a glass-liquid transition at Bg. 相似文献
7.
B. I. Belevtsev V. B. Krasovitsky D. G. Naugle K. D. D. Rathnayaka Glenn Agnolet I. Felner 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1049-1052
Magnetic and superconducting properties of polycrystalline samples of RuSr2Gd1.5Ce0.5Cu2O(10 − δ), asprepared (by solid-state reaction) and annealed in pure oxygen at different pressure are presented. Specific heat and
magnetization were investigated in the temperature range 1.8–300 K with a magnetic field up to 8 T. Specific heat, C (T), shows a jump at the superconducting transition (with onset at T ≈ 37.5 K) and a Schottky-type anomaly below 20 K. It is found that curves C(T) taken for different values of magnetic field have the same crossing point (at T
* ≈ 2.7 K) for all samples studied. At the same time, C(H) curves taken for different temperatures have a crossing point at a characteristic field H
* ≈ 3.7 T. These effects are manifestations of the crossing-point phenomenon, which is supposed to be inherent for strongly
correlated electron systems. 相似文献
8.
Yu. N. Ovchinnikov A. M. Dyugaev 《Journal of Experimental and Theoretical Physics》1999,88(4):696-709
The magnetic field dependence of the average spin of a localized electron coupled to conduction electrons with an antiferromangetic
exchange interaction is found for the ground state. In the magnetic field range μH∼0.5T
c
(T
c
is the Kondo temperature) there is an inflection point, and in the strong magnetic field range μH≫T
c
, the correction to the average spin is proportional to (T
c
/μ H)2. In zero magnetic field, the interaction with conduction electrons also leads to the splitting of doubly degenerate spin
impurity states.
Zh. éksp. Teor. Fiz. 115, 1263–1284 (April 1999)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor 相似文献
9.
Anomalous behavior of the interlayer resistance of a BSCCO-2212 crystal in a parallel magnetic field
V. N. Zavaritskii 《JETP Letters》1996,63(2):139-145
The electrical resistance across the Cu-O layers of a BSCCO-2212 single crystal is investigated in the range of angles 0°⩽φ⩽90°
between the magnetic field H⩽15 T and the ab plane. It is found that the temperature dependence R(T) at the transition into the mixed state is much sharper for φ≃0° than for 1°≲φ≲90°, where R is determined by the perpendicular component of the magnetic field and is described by the Arrhenius law R∼exp(−U/T). For H∥ ab hysteretic jumps in R(T, H), which vanish as the current increases, are observed at fields in the range 5.5⩽H⩽11 T. This effect can be attributed to
a commensurate phase transition in a lattice of Josephson vortices.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 123–128 (25 January 1996) 相似文献
10.
N. E. Sluchanko A. N. Azarevich A. V. Bogach V. V. Glushkov S. V. Demishev A. V. Kuznetsov K. S. Lyubshov V. B. Filippov N. Yu. Shitsevalova 《Journal of Experimental and Theoretical Physics》2010,111(2):279-284
The galvanomagnetic properties of single-crystal samples with various isotopic boron compositions have been investigated for
the first time for the normal state of superconductor LuB12 (T
c ≈ 0.44 K). Precision measurements of the resistivity, Hall coefficient, and magnetic susceptibility have been performed over
a wide temperature range of 2–300 K in magnetic fields up to 80 kOe. A change of the charge transport regime in this nonmagnetic
compound with metallic conduction is shown to occur near T* ≈ 50−70 K. As a result, a sharp peak with significantly different amplitudes for Lu10B12 and Lu11B12 is recorded in the temperature dependences of the Hall coefficient R
H(T) near T*. A significant (about 10%) difference (in absolute value) of the Hall coefficients R
H for the Lu10B12 and Lu11B12 compounds at helium and intermediate temperatures has been found and the patterns of behavior of the dependence R
H(H) for T < T* in an external magnetic field H ≤ 80 kOe for Lu10B12 and Lu11B12 are shown to differ significantly. Analysis of the Curie-Weiss contribution to the magnetic susceptibility χ(T) leads to the conclusion about the formation of magnetic moments μeff ≈ (0.13−0.19)μB in each unit cell of the fcc structure of LuB12 compounds with various isotopic compositions. The possibility of the realization of an electronic topological 2.5-order transition
near T* and the influence of correlation effects in the 5d-band on the formation of a spin polarization near the rare-earth ions in LuB12 is discussed. 相似文献
11.
Electrical conductivity and dielectric properties of single-crystal TlGaSe2 have been studied as a function of γ irradiation dose in the 100–280 K range including the existence of an incommensurate phase. Anomalies in the form of maxima
have been observed in the σ=f(T), tan δ=f(T), and ɛ=f(T) curves at the points of transition from the paraphase to incommensurate (IC) phase, T
i, and from the IC to commensurate phase, T
c. The increase in the quantities σ, tan δ, and ɛ observed initially with increasing irradiation dose is followed by their strong decrease and disappearance of the anomalies.
It has been established that γ irradiation does not affect the phase transition temperatures T
i and T
c.
Fiz. Tverd. Tela (St. Petersburg) 40, 1328–1331 (July 1998) 相似文献
12.
H.-F. Li Y. Su Y. G. Xiao J. Persson P. Meuffels Th. Brückel 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(2):149-157
A neutron powder diffraction (NPD) study on the crystal and magnetic structure of a crushed La1-xSrxMnO3 (x ≈ 1/8) single crystal has been performed. The sample belongs to orthorhombic (Pnma, O) above the Jahn-Teller (JT) transition temperature (TJT) and monoclinic (P121/c1, M′) in the JT regime. We have also refined the NPD data below the charge/orbital ordering (CO/OO) temperature (TCO/OO) with a monoclinic (P121/c1, M′′) model because the experimental resolution was insufficient to clearly identify a triclinic structure. The refined lattice parameters show an obvious breathing-mode distortion between TCO/OO and TJT, accompanied by a large deviation of the monoclinic angle β from 90°, signifying a very strong cooperative JT distortion.
A ferromagnetic (FM) moment of 3.43(5)μ
B/Mn besides an A-type antiferromagnetic (A-AFM) moment of 0.54(2) μ
B/Mn is directed mainly along the b axis in P121/c1 symmetry at 5 K. With increasing temperature, the A-AFM domains transform into FM ones above ~100 K and the FM spin orientation
turns from the b to the c axis in crystallographic b-c plane below Tc = 187(1) K. The magnetization measurements show typical anomalies around TCO/OO and TJT. The measured saturation moment of 3.9(1)μ
B/Mn at 70 kOe and 5 K is well consistent with the sum 3.97(5)μ
B/Mn of the refined FM and A-AFM moments at 5 K, implying the A-AFM spins are aligned in field direction at 70 kOe. The applied
magnetic field can affect the paramagnetic insulating (PMI) state in the range of magnetic polarons. Based on the size of
JT distortion and the bond-valence sums (BVS’s), the CO/OO phenomenon is being discussed. 相似文献
13.
V. P. D’yakonov V. I. Markovich V. L. Kovarskii A. V. Markovich M. Borowiec A. Jendrzejczak H. Szymczak 《Physics of the Solid State》1999,41(3):440-444
The investigation of the specific heat of a RbDy(WO4)2 single crystal at temperatures 0.2–2.5 K and in magnetic fields up to 2 T are reported. The temperature dependence of the
specific heat near T
N=0.818 K is compared with the predictions for different models. The 2D Ising model describes satisfactorily C(T) below T
N, while for T>T
N none of the theoretical models agree with the behavior of C(T) of RbDy(WO4)2. The H-T phase diagram for H∥c is complicated and possesses a triple point, where regions of existence of three magnetic phases converge. The magnetic ordering
is analyzed from the standpoint of the Jahn-Teller nature of the structural phase transitions occurring in RbDy(WO4)2 at higher temperatures. It is shown that the form of the phase diagram depends on the direction of the vector H, for the general case of an arbitrary direction of H, two phase transitions can occur with increasing field.
Fiz. Tverd. Tela (St. Petersburg) 41, 491–496 (March 1999) 相似文献
14.
A. U. Sheleg K. V. Iodkovskaya S. V. Rodin V. A. Aliev 《Physics of the Solid State》1997,39(6):975-977
The influence of γ irradiation on the electrical conductivity σ, the dielectric permittivity ɛ, and the dielectric loss tangent tanδ of β-TlInS2 crystals is investigated in the temperature range of the incommensurate phase. It is established that γ irradiation lowers the values of ɛ and tanδ over the entire investigated temperature range and decreases the maxima of the σ(T) and tanδ(T) curves in the vicinity of the transition temperature T
c, but does not alter the transition temperature.
Fiz. Tverd. Tela (St. Petersburg) 39, 1088–1090 (May 1997) 相似文献
15.
The field dependence of the vibrational contribution to the dynamic magnetic permeability μ
V(H) is calculated for a thin (of thickness d∼λ) high-T
c superconducting wafer in a magnetic field parallel to the surface. The resulting curves are plotted on the basis of an exact
numerical analysis of the vortex structures both for the thermodynamic-equilibrium vortex lattice and in the presence of pinning
forces and the Bean-Livingston surface barrier. It is shown that the μ
V(H) curves are highly sensitive to the size factor (d/λ) and exhibit abrupt changes corresponding to a change in the number of vortex rows. The equilibrium μ
V(H) curve is found to be similar in its general behavior and absolute value (obtained with allowance for the distribution of
grain sizes and with appropriate values of λ and ϰ) to the experimental μ
V(H) curve plotted at nitrogen temperature for fine-grained YBa2Cu3Ox with grain diameters 〈D〉∼λ in an increasing magnetic field. It is established that the main cause of the experimentally observed irreversible behavior
of the μ
V(H) curves during cyclic variation of the applied magnetic field is the existence of a surface barrier to the exit of vortices
from the superconductor. The lower limit H
min(B) of stability of the mixed state in the presence of an ideal surface barrier in a thin, high-T
c superconducting wafer (d∼λ) is determined, along with the range of the vortex state (H
max-H
min) for a fixed number of vortices in micrometer-size grains of the investigated YBaCuO samples.
Fiz. Tverd. Tela (St. Petersburg) 39, 1943–1947 (November 1997) 相似文献
16.
The temperature R(T) and field R(H) dependences of the electrical resistance in the compound Eu0.7
A
0.3MnO3 (A=Ca, Sr) are investigated in the temperature range 4.2–200 K in magnetic fields up to 14 T. Above the antiferromagnetic transition
temperature T
a, the function R(T) is semiconducting in character. Application of a magnetic field H that exceeds a certain critical value H
c changes the character of the function R(T) for Eu0.7Sr0.3MnO3 to metallic (dR/dT>0). For T<T
a and H<H
c a jump in the resistance is observed indicating instability of the electronic state caused by competition between charge
and spin ordering of the Mn ions of different valences.
Fiz. Tverd. Tela (St. Petersburg) 40, 708–712 (April 1998) 相似文献
17.
V. A. Moshnikov A. V. Moshnikov A. I. Rumyantseva S. A. Nemov R. V. Parfen’ev A. V. Chernyaev 《Physics of the Solid State》1999,41(4):550-555
A reliable technique of local chemical characterization of multicomponent semiconductor solid solutions has been developed,
and the possibility of its application to the SnTe-SnSe quaternary solid solutions doped with 16 at.% In verified. The behavior
of the electrical resistivity of samples of these solid solutions at low temperatures, 0.4–4.2 K, has been studied. The critical
temperature T
c and the second critical magnetic field H
c2 of the superconducting transition and their dependences on the solid-solution composition have been determined. The superconducting
transition at T
c≈2–3 K is due to hole filling of the In-impurity resonance states, and the observed variation of the superconducting transition
parameters with increasing Se content in the solid solution is related to the extrema in the valence band and the In band
of resonance states shifting with respect to one another.
Fiz. Tverd. Tela (St. Petersburg) 41, 612–617 (April 1999) 相似文献
18.
Y. Kopelevich V. V. Lemanov S. Moehlecke J. H. S. Torres 《Physics of the Solid State》1999,41(12):1959-1962
Measurements of the basal-plane resistivity ρ
a(T,H) performed on highly oriented pyrolitic graphite, with magnetic field H∥c-axis in the temperature interval 2–300K and fields up to 8 T, provide evidence for the occurrence of both field-induced and
zero-field superconducting instabilities. Additionally, magnetization M(T,H) measurements suggest the occurrence of Fermi surface instabilities which compete with the superconducting correlations.
Fiz. Tverd. Tela (St. Petersburg) 41, 2135–2138 (December 1999) 相似文献
19.
Yu. N. Ovchinnikov 《Journal of Experimental and Theoretical Physics》1997,85(4):818-823
It is shown that near the transition temperature T
c the coefficients of the second and third terms in the expansion of the free energy in powers of H
c2−B (B is the magnetic field induction inside the superconductor) go to zero simultaneously for a value of κ=1 for the Ginzburg-Landau parameter. Thereby the structure of the mixed state near H
c2 for a value of the parameter κ close to unity is determined by the temperature correction to the coefficient for the third power and the coefficient for
the fourth power in the expansion of the free energy in powers of H
c2−B. The values of these coefficients depend on the type of vortex lattice.
Zh. éksp. Teor. Fiz. 112, 1499–1509 (October 1997) 相似文献
20.
S. V. Demishev A. V. Semeno N. E. Sluchanko N. A. Samarin A. N. Vasil’ev L. I. Leonyuk 《Journal of Experimental and Theoretical Physics》1997,85(5):943-948
Resonant absorption of microwaves in CuGeO3 single crystals in a frequency band of 40 to 120 GHz, in magnetic field B⩽15 T, at temperatures ranging between 0.5 and 300 K, and in the configuration B∥a has been investigated. Several absorption lines (S
0, S
a, and S
b) whose parameters strongly depend on temperature have been detected close to ESR. The temperature dependence of the total
absorption in the main line S
0 with the Landé g-factor g
0=2.154 at temperatures above the spin-Peierls transition temperature is in good agreement with Bonner and Fisher’s theoretical
prediction for a one-dimensional Heisenberg spin chain. In addition to the main resonance, a resonance of smaller amplitude,
S
a, with the g-factor g
a=2.72 has been detected at temperatures ranging down to a characteristic temperature T≃1 K, below which the amplitude of this feature drops to zero. A radical restructuring of the magnetoabsorption spectrum occurs
at the temperature of the spin-Peierls transition T
SP≈14 K. At T<12 K new features emerge in the spectrum, namely, a broad absorption line overlapping with the narrow lines S
0 and S
a, and a line S
b with g
b=1.83, which is not detected at temperatures above T
SP. An analysis of amplitudes and total absorption of ESR lines as functions of temperature has shown that the temperature range
below 1 K is anomalous, which may be caused by an additional ordering in the CuGeO3 magnetic subsystem at low temperatures.
Zh. éksp. Teor. Fiz. 112, 1727–1738 (November 1997) 相似文献