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1.
A. Yu. Mollaev I. K. Kamilov R. K. Arslanov T. R. Arslanov U. Z. Zalibekov V. M. Novotortsev S. F. Marenkin 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(8):1107-1108
The dependences of the longitudinal magnetoresistance (Δρ
zz
/ρ0)(P), transverse magnetoresistance (Δρ
xx
/ρ0)(P), and magnetic susceptibility (χ/χ0(P)) on hydrostatic pressure P ≤ 7 GPa in the ferromagnetic semiconductor Cd0.7Mn0.3GeAs2 at room temperature were investigated. 相似文献
2.
L. S. Lobanovskii V. M. Novotortsev S. F. Marenkin V. M. Trukhan T. V. Shelkovaya 《JETP Letters》2009,89(7):333-336
The magnetic and electric properties of a Cd0.90Mn0.10GeAs2 solid solution with the chalcopyrite structure have been investigated in wide temperature and field ranges. It has been found that a metamagnetic transition from a low-magnetization state to a high-magnetization one is initiated in Cd0.90Mn0.10GeAs2 near the magnetic ordering temperature. This transition is accompanied by the hysteresis of magnetic properties. An external magnetic field at temperatures above T C also induces the metamagnetic transition. When the temperature increases above T C, the magnetization jump decreases, whereas fields inducing the metamagnetic transition increase. The band character of magnetism and metamagnetism in the effective magnetic field is assumed on the basis of the behavior of magnetization in the metamagnetic transition and analysis of the band structure of the solid solution of cadmium-germanium diarsenide with manganese. 相似文献
3.
G. A. Politova I. S. Tereshina G. S. Burkhanov O. D. Chistyakov V. B. Chzhan V. I. Nizhankovskii A. Zaleski T. P. Kaminskaya V. V. Popov 《Physics of the Solid State》2011,53(10):2028-2031
A complex investigation of the structural, magnetic, and magnetothermal properties of the Tb0.3Dy0.7Co2 compound synthesized with the use of high-purity rare-earth metals has been performed. The phase composition has been controlled
using the X-ray structural analysis, and the topology of the alloy surface has been investigated using atomic-force microscopy.
It has been established that the Tb0.3Dy0.7Co2 compound is single-phase, while the samples selected for measurements possess a clearly pronounced texture. The magnetization
has been measured using a vibrating-sample magnetometer in the fields up to 100 kOe in a temperature range from 4.2 to 200
K. The Curie temperature of the compound is 170 K. The data on the temperature dependence of heat capacity of Tb0.3Dy0.7Co2 have been obtained. The magnetocaloric effect ΔT has been measured by a direct method in the fields up to 18 kOe applied both along and perpendicularly to the texture axis.
The anisotropic behavior of the magnitude ΔT for this compound, which possesses the cubic structure, has been found. The maximum value of the magnetocaloric effect ΔT = 2.3 K (ΔH = 18 kOe) has been observed upon applying the magnetic field along the texture axis. 相似文献
4.
Yu. G. Chukalkin A. E. Teplykh A. N. Pirogov D. G. Kellerman 《Physics of the Solid State》2010,52(12):2545-2551
The specific features of the crystal structure and the magnetic state of stoichiometric lithium manganite in the structurally
ordered Li[Mn2]O4 and disordered Li1 − δMnδ[Mn2 − δLiδ]O4 (δ = 1/6) states have been investigated using neutron diffraction, X-ray diffraction, and magnetic methods. The structurally
disordered state of the manganite was achieved under irradiation by fast neutrons (E
eff ≥ 1 MeV) with a fluence of 2 × 1020 cm−2 at a temperature of 340 K. It has been demonstrated that, in the initial sample, the charge ordering of manganese ions of
different valences arises at room temperature, which is accompanied by orthorhombic distortions of the cubic spinel structure,
and the long-range antiferromagnetic order with the wave vector k = 2π/c(0, 0, 0.44) is observed at low temperatures. It has been established that the structural disordering leads to radical changes
in the structural and magnetic states of the LiMn2O4 manganite. The charge ordering is destroyed, and the structure retains the cubic symmetry even at a temperature of 5 K. The
antiferromagnetic type of ordering transforms into ferrimagnetic ordering with local spin deviations in the octahedral sublattice
due to the appearance of intersublattice exchange interactions. 相似文献
5.
D. P. Kozlenko T. A. Chan S. E. Kichanov Z. Jirák L. S. Dubrovinsky B. N. Savenko 《JETP Letters》2011,92(9):590-594
The crystal structure and Raman spectra of Pr0.7Ca0.3MnO3 manganite at high pressures of up to 30 GPa and the magnetic structure at pressures of up to 1 GPa have been studied. A structural
phase transition from the orthorhombic phase of the Pnma symmetry to the high-pressure orthorhombic phase of the Imma symmetry has been observed at P ∼ 15 GPa and room temperature. Anomalies of the pressure dependences of the bending and stretching vibrational modes have
been observed in the region of the phase transition. A magnetic phase transition from the initial ferromagnetic ground state
(T
C = 120 K) to the A-type antiferromagnetic state (T
N = 140 K) takes place at a relatively low pressure of P = 1 GPa in the low-temperature region. The structural mechanisms of the change of the character of the magnetic ordering
have been discussed. 相似文献
6.
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
7.
D. P. Kozlenko T. A. Chan S. E. Kichanov A. V. Trukhanov S. V. Trukhanov B. N. Savenko 《Physics of Particles and Nuclei Letters》2011,8(10):1063-1065
The crystal and magnetic structures of manganite Pr0.7Ba0.3MnO3 have been studied at high pressures of up to 5.1 GPa and temperatures from 10 to 300 K by means of the neutron diffraction.
At normal pressure and a temperature T
C = 200 K, a ferromagnetic state forms in Pr0.7Ba0.3MnO3. At high pressures P ≥ 1.9 GPa and T < T
N ≈ 153 K, a new antiferromagnetic state of A-type have been observed. Under high pressure, the Curie temperature T
C increases with the characteristic quantity dT
C/dP ≈ 2.4 K/GPa. A possible reason for the appearance of an A-type antiferromagnetic phase in Pr0.7Ba0.3MnO3 at high pressures may be anisotropic uniaxial compression of oxygen octahedra along the b axis of the orthorhombic structure. 相似文献
8.
The magnetic susceptibility χ of Hg
1−x
Mn
x
S is investigated at temperatures T = 77–300 K for H = 4 kOe by the Faraday method before and after thermal treatment of the
sample in compound vapors. The special features of χ are found to be caused by the presence in the crystals of Mn-S-Mn-S clusters of different sizes in which indirect antiferromagnetic exchange interaction of the Mn atoms occurs through the chalcogen atoms. Thermal treatment of samples in compound vapors causes changes of sizes of clusters
existing in the crystal and even dissipation of the second-phase inclusions.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 59–63, March, 2008. 相似文献
9.
M. A. Anisimov A. V. Bogach V. V. Glushkov S. V. Demishev N. A. Samarin V. B. Filipov N. Yu. Shitsevalova A. V. Kuznetsov N. E. Sluchanko 《Journal of Experimental and Theoretical Physics》2009,109(5):815-832
The magnetoresistance Δρ/ρ of single-crystal samples of praseodymium and neodymium hexaborides (PrB6 and NdB6) has been measured at temperatures ranging from 2 to 20 K in a magnetic field of up to 80 kOe. The results obtained have
revealed a crossover of the regime from a small negative magnetoresistance in the paramagnetic state to a large positive magnetoresistive
effect in magnetically ordered phases of the PrB6 and NdB6 compounds. An analysis of the dependences Δρ(H)/ρ has made it possible to separate three contributions to the magnetoresistance for the compounds under investigation. In
addition to the main negative contribution, which is quadratic in the magnetic field (−Δρ/ρ ∝ H
2), a linear positive contribution (Δρ/ρ ∝ H) and a nonlinear ferromagnetic contribution have been found. Upon transition to a magnetically ordered state, the linear
positive component in the magnetoresistance of the PrB6 and NdB6 compounds becomes dominant, whereas the quadratic contribution to the negative magnetoresistance is completely suppressed
in the commensurate magnetic phase of these compounds. The presence of several components in the magnetoresistance has been
explained by assuming that, in the antiferromagnetic phases of PrB6 and NdB6, ferromagnetic nanoregions (ferrons) are formed in the 5d band in the vicinity of the rareearth ions. The origin of the quadratic contribution to the negative magnetoresistance is
interpreted in terms of the Yosida model, which takes into account scattering of conduction electrons by localized magnetic
moments of rare-earth ions. Within the approach used, the local magnetic susceptibility χloc has been estimated. It has been demonstrated that, in the temperature range T
N < T < 20 K, the behavior of the local magnetic susceptibility χloc for the compounds under investigation can be described with good accuracy by the Curie-Weiss dependence χloc ∝ (T − Θ
p
)−1. 相似文献
10.
A. A. Blinkin V. V. Derevyanko T. V. Sukhareva V. L. Uvarov V. A. Finkel Yu. N. Shakhov I. N. Shlyakhov 《Physics of the Solid State》2011,53(2):245-255
This paper reports on the results of investigations of the influence of irradiation of the two-band BCS superconductor MgB2 by electrons with an average energy $
\bar {\rm E}
$
\bar {\rm E}
∼ 10 MeV at high doses (0 ≤ ϕt ≤ ∼2.5 × 1018 cm−2) on the temperature and width of the transition to the superconducting state, the temperature dependence of the electrical
resistivity in the normal state, the crystal lattice parameters, and the diffraction line intensity. An increase in the electron
irradiation dose ϕt leads to the following effects: a decrease in the critical temperature T
c
; an increase in the width of the superconducting transition ΔT
c
; and a decrease in the “residual electrical resistivity” ρ273 K/ρ40 K, in the parameters a and c of the hexagonal crystal lattice, and in the ratio between the diffraction line intensities I
110/I
100. From analyzing the results obtained, it has been established that the main type of radiation damages under irradiation of
the BCS superconductor MgB2 by high-energy electrons is the formation of vacancies in the B sublattice, which leads to a narrowing of the large band
gap Δσ on the Fermi surface. 相似文献
11.
I. Yu. Gaidukova S. A. Granovskiy A. S. Markosyan 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1373-1375
Results from studies of the crystal structure, resistivity, susceptibility, and magnetization of nonstoichiometric Ni50Mn50 − x
In
x
Heusler alloys are presented. Anomalous effects discovered in temperature dependences can be interpreted as the influence
of the frustrated magnetic state exhibited by manganese moments in the martensitic phase. A field-induced phase transition
to the austenitic phase was observed for several concentrations around room temperature. 相似文献
12.
Y. B. Lin Z. G. Huang Y. M. Yang S. Wang S. D. Li F. M. Zhang Y. W. Du 《Applied Physics A: Materials Science & Processing》2011,104(1):143-147
(La0.7Sr0.3MnO3)
x
/(YBa2Cu3O7)
y
composites were prepared by mixing La0.7Sr0.3MnO3 powders and the sol–gel-derived YBa2Cu3O7 matrix, followed by high-temperature calcinations. Their structural, magnetic properties and magnetoresistance effect have
been investigated systematically. A giant positive magnetoresistance (PMR) at low magnetic field is observed at low temperatures.
In the case of (La0.7Sr0.3MnO3)1/(YBa2Cu3O7)9 composite, the PMR achieves 260% under a magnetic field of 5800 Oe. However, the PMR value sharply decreases with increasing
temperature and no magnetoresistance effects are found above metal-insulator transition temperature. The enhancement of spin-dependent
scattering at the grain boundaries should be responsible for the observed PMR. In addition, the temperature dependence of
resistance under magnetic field could be explained by the competition between diamagnetism and paramagnetism in YBCO phase.
At low temperature, the diamagnetism is predominant over paramagnetism and the interface scattering between LSMO grains is
enhanced correspondingly. As a result, the low-temperature resistance increases and large PMR appears. 相似文献
13.
S. V. Trukhanov A. V. Trukhanov A. N. Vasiliev H. Szymczak 《Journal of Experimental and Theoretical Physics》2010,111(2):209-214
The magnetic and thermal properties of the anion-deficient La0.70Sr0.30MnO2.85 manganite are investigated in wide temperature (4–350 K) range, including under hydrostatic pressure (0–1.1 GPa). Throughout
the pressure range investigated, the sample is spin glass with diffused phase transition into paramagnetic state. It is established,
that spin glass state is a consequence of exchange interaction frustration of the ferromagnetic clusters embeded into antiferromagnetic
clusters. The magnetic moment freezing temperature T
f
of ferromagnetic clusters increases under pressure, freezing temperature dependence on pressure is characterized by derivative
value ∼4.5 K/GPa, while the magnetic ordering T
MO temperature dependence is characterized by derivative value ∼13 K/GPa. The volume fraction of sample having ferromagnetic
state is V
fer ∼ 13% and it increases under a pressure of 1.1 GPa by ΔV
fer ≈ 6%. Intensification of ferromagnetic properties of the anion-deficient La0.70Sr0.30MnO2.85 manganite under hydrostatic pressure is a consequence of oxygen vacancies redistribution and unit cell parameters decrease.
The most likely mechanism of frustrated exchange interactions formation is discussed. 相似文献
14.
H.-F. Li Y. Su Tapan Chatterji A. Nefedov J. Persson P. Meuffels Y. Xiao D. Vaknin Th. Brückel 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,74(4):457-461
Soft X-ray resonant scattering studies at the Mn LII, III- and the La MIV, V- edges of single-crystal LaSr2Mn2O7 are
reported. At low temperatures, below TN ≈ 160 K, energy scans with a fixed momentum transfer at the A-type antiferromagnetic (0 0
1) reflection around the Mn LII, III-edges with incident linear σ and π polarizations show strong resonant enhancements. The
splitting of the energy spectra around the Mn LII, III-edges may indicate the presence of a mixed valence state, e.g., Mn3+/Mn4+.
The relative intensities of the resonance and the clear shoulder-feature as well as the strong incident σ and π polarization
dependences
strongly indicate its complex electronic origin. Unexpected enhancement of the charge Bragg (0 0 2) reflection at the La MIV, V-edges with
σ polarization has been observed up to 300 K, with an anomaly appearing around the orbital-ordering transition temperature,
TOO ≈
220 K, suggesting a strong coupling (competition) between them. 相似文献
15.
L. Seetha Lakshmi K. Dörr K. Nenkov A. Handstein V. S. Sastry K.-H. Müller 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):115-121
We report the charge state modification effects at the Mn site on the ground
state properties of colossal magnetoresistive manganites. Ta5+
substitution results in an appreciable increase in the lattice parameters
and unit cell volume due to increased Mn3+ concentration. The
ferromagnetic-metallic ground state modifies to a cluster glass insulator
for
. The reduction in the transition temperatures with
increasing x is ∼39 K/at.%. Besides the modification of majority carrier concentration due to increased Mn3+ concentration and enhanced local structural effects, the local
electrostatic potential of the substituent seems to contribute to the
unusually strong reduction of the transition temperatures of the compounds.
Thermo magnetic irreversibility just below Curie temperature (Tc),
non-saturation of magnetization, two distinct magnetic transitions in ac
susceptibility in an appropriate static field: close to Tc and other at
low temperature (the spin freezing temperature (Tg)) and non-stationary
dynamics with a characteristic maximum in the magnetic viscosity close to
Tg confirm a cluster glass state for
. These results
find additional support from a linear low temperature magnetic specific heat
of x = 0.10 with a characteristic broad maximum close to Tg. 相似文献
16.
Magnetic and thermal properties of CuFeS<Subscript>2</Subscript> at low temperatures 总被引:1,自引:0,他引:1
The magnetic moment M, the magnetic susceptibility χ, and the thermal conductivity of chalcopyrite CuFeS2, which is a zero-gap semiconductor with antiferromagnetic ordering, have been measured in the temperature range 10–310 K.
It has been revealed that the quantities χ(T) and M(T) increase anomalously strongly at temperatures below ∼100 K. The temperature dependence M(T) is affected by the magnetic prehistory of the sample. An analysis has demonstrated that the magnetic anomalies are associated
with the presence of a system of noninteracting magnetic clusters in the CuFeS2 sample under investigation. The formation of the clusters is most likely caused by the disturbance of the ordered arrangement
of Fe and Cu atoms in the metal sublattice of the chalcopyrite, which is also responsible for the phase inhomogeneity of the
crystal lattice. The inhomogeneity brings about strong phonon scattering, and, as a result, the temperature dependence of
the thermal conductivity coefficient exhibits a behavior characteristic of partially disordered crystals. 相似文献
17.
We report measurements of the temperature dependence of the electrical resistivity, ρ(T), and magnetic pen-etration depth, λ(T), for polycrystalline samples of Eu0.5K0.5Fe2As2 with T
c
= 31 K. ρ(T) follows a linear temperature dependence above T
c
and bends over to a weaker temperature dependence around 150 K. The magnetic penetration depth, determined by radio frequency
technique displays an unusual minimum around 4 K which is associated with short-range ordering of localized Eu3+ moments.
The article is published in the original. 相似文献
18.
L. S. Ewe I. Hamadneh H. Salama N. A. Hamid S. A. Halim R. Abd-Shukor 《Applied Physics A: Materials Science & Processing》2009,95(2):457-463
The magnetotransport and magnetoresistive (MR) properties of manganese-based La0.67Ca0.33MnO3 perovskite with different grain sizes are reported. The electrical resistivity was measured as a function of temperature
in magnetic fields of 0.5 and 1 T. The insulator–metal transition temperature, T
IM, shifted to a higher temperature with the application of the magnetic field. In zero field, T
IM is almost constant (∼271 K) for all samples except for the sample with the largest grain size, where T
IM=265 K. The temperature dependence of resistivity was fitted with several equations in the metallic (ferromagnetic) region
and the insulating (paramagnetic) region. The density of states at the Fermi level, N(E
F), and the activation energy of electron hopping were estimated by fitting the resistivity versus temperature curves. The
ρ–T
2 curves are nearly linear in the metallic regime, but the ρ–T
2.5 curves exhibit a deviation from linearity. The variable range hopping model and small polaron hopping model fit the data
well in the high-temperature region, indicating the existence of the Jahn–Teller distortion that localizes the charge carriers.
MR was found to increase with an increase in the magnetic field, an effect which is attributed to the intergrain spin tunneling
effect. 相似文献
19.
A. V. Malakhovskii E. V. Eremin D. A. Velikanov A. V. Kartashev A. D. Vasil’ev I. A. Gudim 《Physics of the Solid State》2011,53(10):2032-2037
The magnetic properties of the Nd0.5Gd0.5Fe3(BO3)4 single crystal have been studied in principal crystallographic directions in magnetic fields to 90 kG in the temperature
range 2–300 K; in addition, the heat capacity has been measured in the range 2–300 K. It has been found that, below the Néel
temperature T
N = 32 K down to 2 K, the single crystal exhibits an easy-plane antiferromagnetic structure. A hysteresis has been detected
during magnetization of the crystal in the easy plane in fields of 1.0–3.5 kG, and a singularity has been found in the temperature
dependence of the magnetic susceptibility in the easy plane at a temperature of 11 K in fields B < 1 kG. It has been shown that the singularity is due to appearance of the hysteresis. The origin of the magnetic properties
of the crystal near the hysteresis has been discussed. 相似文献
20.
Large low-field-induced magnetic entropy changes, ΔS
M, are observed in La0.67Ca0.33MnO3 and La0.67Ca0.33Mn0.96Fe0.04O3 single crystals. The peaks of ΔS
M broadened asymmetrically to high temperatures under higher magnetic fields for two materials should be attributed to the
first-order magnetic phase transition at T
c. A small amount of iron doping results in an increase in the refrigerant capacity of the material though the magnetic entropy
change decreases. The discovery of excellent magnetocaloric features of these single crystals in the low magnetic field can
provide some ideas for exploring novel magnetic refrigerants operating under permanent magnet rather than superconducting
one as magnetic field source.
Supported by the State Key Project of Fundamental Research (Grant No. 2005CB724402), and the National Natural Science Foundation
of China (Grant No. 50672126)
Contributed by CHENG ZhaoHua 相似文献