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1.
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
2.
M. Patra K. De S. Majumdar S. Giri 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):367-371
We observe the negative shift of the magnetic hysteresis loop at 5 K, while the sample is cooled in external magnetic field
in case of 30% of Fe substitution in LaMnO3. The negative shift and training effect of the hysteresis loops indicate the phenomenon of exchange bias. The cooling field
dependence of the negative shift increases with the cooling field below 7.0 kOe and then, decreases with further increase
of cooling field. The temperature dependence of the negative shift of the hysteresis loops exhibits that the negative shift
decreases sharply with increasing temperature and vanishes above 20 K. Temperature dependence of dc magnetization and ac susceptibility
measurements show a sharp peak (Tp) at 51 K and a shoulder (Tf) around 20 K. The relaxation of magnetization shows the ferromagnetic and glassy magnetic components in the relaxation process,
which is in consistent with the cluster-glass compound. 相似文献
3.
The magnetic and electrical properties of metallic glasses with the general formula Fe85-xCoxB15 were investigated over a large temperature range to study their concentration-dependent physical parameters. All of the samples investigated (x=17,21,30, and 40) were soft ferromagnets with coercive fields Hc1 Oe and high Curie temperatures slightly above 1200 K. The temperature-dependent magnetization behaved irregularly, and exhibited hysteresis during heating and subsequent cooling through the Curie temperature. The variation of the magnetization with temperature demonstrates that one or more phase transformations (crystallization) occurred in the course of the heating. The electrical resistivities exhibited positive temperature coefficients and minima at temperatures below 50 K. We did not observe a nonmonotonic variation of the magnetic and electrical properties with a monotonic change of the Fe85-xCoxB15 composition that would correlate with the earlier proposed formation of strong nanoclusters in the vicinity of particular stoichiometrically close Fe:Co ratios. The good soft magnetic characteristics make the Fe85-xCoxB15 metal glasses promising candidates for engineering materials in inductive applications. PACS 71.23.Cq; 75.75.+a 相似文献
4.
“Zero field”-Mössbauer and magnetization measurements have been performed on an amorphous Fe76Mo8Cu1B15 alloy in the temperature range of (10-340) K. The room-temperature Mössbauer spectrum exhibits magnetic dipole and electric quadrupole interactions. At approximately 306 K, the magnetic interactions vanish and the alloy shows fully paramagnetic behavior. On the other hand, the relative representation of paramagnetic component becomes weak with decreasing temperature and below 220 K the magnetic dipole interactions prevail. Below this temperature an anomaly in the low-temperature dependencies of ac susceptibility and of magnetization, measured during cooling the specimen from 340 K down to 20 K is observed. The anomaly on the magnetization curve vanishes in the field of 200 Oe. 相似文献
5.
(NH4)3NbOF6 single crystals were grown, polarization-optical studies were performed, and birefringence was measured over the temperature range 90–500 K. A sequence of first-order structural phase transitions was found at temperatures T 1↓ = 259.7 K and T 2↓ = 257.7 K with temperature hysteresis δT 1 = 0.9 K and δT 2 = 1.9 K. The transitions are accompanied by twinning and the following change in the crystal symmetry: cubic ? tetragonal ? monoclinic. Optical second harmonic generation is found to occur at room temperature, which indicates that the cubic phase is not centrosymmetric. It is assumed that the phase transitions are ferroelastic and ferroelectric in nature. 相似文献
6.
R. I. Zainullina N. G. Bebenin V. V. Mashkautsan V. V. Ustinov Ya. M. Mukovskii A. A. Arsenov 《Physics of the Solid State》2003,45(9):1754-1758
An experimental study of the temperature behavior of longitudinal sound velocity, internal friction, electrical resistivity, and thermopower of single-crystal La0.75Ba0.25MnO3 is reported. A structural transition accompanied by a large jump (18%) in the sound velocity was found to occur at T S ≈170 K. Within the interval 156–350 K, the temperature dependences of the sound velocity and internal friction reveal a temperature hysteresis. An internal-friction peak due to relaxation processes was detected. The metallic and semiconducting regions are separated by a transition domain about 80 K wide lying below the Curie temperature T C =300 K. 相似文献
7.
N. A. Zhuravlev N. A. Mukhina D. G. Kellerman V. S. Gorshkov 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(11):1522-1524
The processes of lithium redistribution in the structure of cubic Li4Ti5O12 spinel, caused by both chromium doping and thermal activation, have been investigated by nuclear magnetic resonance. It is
shown that Li ions migrate from tetra- to octahedral crystallographic positions with an increase in temperature. This process
becomes more pronounced at temperatures above 400 K. In contrast, the fraction of tetrahedrally coordinated Li increases as
a result of doping with chromium. 相似文献
8.
A. I. Pankrats G. A. Petrakovskii M. A. Popov K. A. Sablina L. A. Prozorova S. S. Sosin G. Szimczak R. Szimczak M. Baran 《JETP Letters》2003,78(9):569-573
The static and resonance properties of copper metaborate CuB2O4 were experimentally studied in a magnetic field applied in the crystal tetragonal plane. The field-induced second-order phase transition to a weakly ferromagnetic state was observed in the temperature range 10–20 K. The low-field state is characterized by the absence of spontaneous moment, and it represents, presumably, a long-period helicoid. At temperatures below 2 K, two sequential first-order phase transitions were observed. They were accompanied by jumps in resonance absorption with a hysteresis upon changing field-scan direction. These transitions can be caused by the transformation of the incommensurate spin structure into the helicoidal states with periods commensurate with the lattice translation period. 相似文献
9.
A. Yu. Mollaev I. K. Kamilov R. K. Arslanov T. R. Arslanov U. Z. Zalibekov V. M. Novotortsev S. F. Marenkin 《JETP Letters》2010,91(9):478-480
The magnetic susceptibility χ/χ0 and the longitudinal Δρ
zz
/ρ0 and transverse Δρ
xx
/ρ0 magnetoresistances have been measured as functions of the hydrostatic pressure P ≤ 7 GPa at room temperature in the high-temperature ferromagnetic semiconductor Cd0.7Mn0.3GeAs2 with a chalcopyrite structure and the Curie temperature T
c = 355 K. A pressure-induced metamagnetic transition from the low-magnetization state to the high-magnetization state has
been observed in Cd0.7Mn0.3GeAs2 near the magnetic ordering temperature. This transition is accompanied by the hysteresis of the magnetic susceptibility and
magnetoresistance. 相似文献
10.
The surface of SrFe12O19 coated with a CoO layer reveals a strong exchange bias characterized by magnetic hysteresis loops. The low-temperature coercivity, HC, and the squareness, MR/MS, of a permanent magnet of SrFe12O19/CoO powder prepared by the sol–gel method are enhanced after field cooling through the Néel temperature (TN=290 K) when compared to those after zero-field cooling. The existence of loop shifts and the enhancement of HC indicate that exchange-bias effects, which are induced by the ferromagnetic/antiferromagnetic (FM/AFM) exchange-coupling interactions, are responsible for these behaviors. According to our experimental results, some of the factors controlling the exchange bias, such as FM/AFM interfaces and the CoO amount of the antiferromagnetic layer, are discussed. PACS 75.30.Et; 75.50.Ee; 75.60.Ej; 75.60.Gm; 75.70.Cn 相似文献
11.
A. V. Pavlenko I. N. Zakharchenko A. S. Anokhin Yu. A. Kuprina L. I. Kiseleva Yu. I. Yuzyuk 《Physics of the Solid State》2017,59(5):909-913
Solid solution Sr0.5Ba0.5Nb2O6 films have been synthesized on a (111)Pt/(001)Si substrate by rf deposition in an oxygen atmosphere. The depolarized Raman spectra, the structure, and the dielectric characteristics of the films have been studied over a wide temperature range. It is found that the films were singlephase, had the tetragonal tungsten bronze structure, and had a pronounced axial texture with axis 001 directed perpendicular to the substrate surface. It is shown that the film material undergoes a diffuse phase transition to the state of a relaxor ferroelectric in the temperature range 300–425 K. Possible reasons of the regularities observed are discussed. 相似文献
12.
T. V. Kulikova V. A. Bykov A. A. Belozerova K. Yu. Shunyaev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2016,10(2):356-360
We investigate the processes of crystallization and determined the structure and thermal properties of Al86Ni8Ho6 amorphous alloy in a wide temperature range. A three-stage nature of the crystallization process upon heating to a temperature of 700 K is found. According to data of high-temperature X-ray diffraction analysis, the crystallization of an Al86Ni8Ho6 amorphous ribbon is rather complex: aluminum crystallites grow in the amorphous phase to a temperature of 470 K, a Ho3Ni5Al19 phase is formed above 563 K, and a HoAl3 phase appears above 598 K. The phases of Ho3Ni5Al19 and HoAl3 are retained up to a temperature of 723 K. A three-stage kinetic model of the crystallization process with the reaction sequence is proposed based on calculations by multivariate nonlinear regression. The values of the total activation energy for each crystallization stage reach 239, 378, and 247 kJ/mol. 相似文献
13.
V. G. Pushin E. B. Marchenkova A. V. Korolev N. I. Kourov E. S. Belosludtseva A. V. Pushin A. N. Uksusnikov 《Physics of the Solid State》2017,59(7):1321-1331
Comparative studies of physical characteristics (the electrical resistivity, the magnetic susceptibility, the magnetization, the bending deformation, and the degree of shape recovery during subsequent heating) of the Ni54Mn21Ga25 ferromagnetic alloy as-cast and rapidly quenched from melt have been performed in the temperature range 2–400 K. The results are compared to the results of studying the structural–phase transformations by transmission and scanning electron microscopy and X-ray diffraction. It is found that the rapid quenching influences the microstructure, the magnetic state, the critical temperatures, and the specific features of thermoelastic martensite transformations in the alloy. It is found that the resource of the alloy plasticity and thermomechanical bending cyclic stability demonstrates a record-breaking increase in the intercritical temperature range and during subsequent heating. 相似文献
14.
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
15.
V. V. Hoang 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(3):291-297
Dynamical heterogeneities (DH) in low density liquid SiO2 have been
investigated by molecular dynamics (MD) method. Simulations were done in the
basic cube under periodic boundary conditions containing 3000 particles with
the pair interatomic potentials, which have a weak electrostatic interaction
and a Morse type short range interaction (PMSI). We have evaluated the
non-Gaussian parameter for the self part of the van Hove correlation
function and we found a clear evidence of the existence of DH in low density
liquid SiO2. Moreover, the atomic displacement distribution (ADD) in a
model has been obtained and it deviates from a Gaussian form. The results
have been compared with those obtained in another liquid SiO2 system
with the Born-Mayer interatomic potentials (BMP) in order to observe the
interatomic potential effects on the DH in the system and indeed, the
effects are strong. Calculations showed that particles of extremely low or
fast mobility have a tendency to form a cluster and mean cluster size of
most mobile and immobile particles in PMSI models increases with decreasing
temperature. In contrast, no systematic changes have been obtained for the
most mobile and immobile particles in BMP models. Calculations show that
there is no relation between local particle environment and particle
mobility in the system. 相似文献
16.
S. Kabi A. Ghosh 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(4):377-381
Electrical complex ac conductivity of the compound
Li0.9[Ni1/3Mn1/3Co1/3]O1.95 has been studied in the
frequency range 10 Hz–2 MHz and in the temperature range 93–373 K. It
has been observed that the frequency dependence of the ac conductivity obeys
a power law and the temperature dependence of the ac conductivity is quite
weak. The experimental data have been analyzed in the framework of several
theoretical models based on quantum mechanical tunneling and classical
hopping over barriers. It has been observed that the electron tunneling is
dominant in the temperature range from 93 K to 193 K. A crossover of
relaxation mechanism from electron tunneling to polaron tunneling is
observed at 193 K. Out of the several models discussed, the electron
tunneling and the polaron tunneling models are quite consistent with the
experimental data for the complex ac conductivity. The various parameters
obtained from the fits of the experimental results for the real and
imaginary parts of the conductivity to the predictions of these models are
quite reasonable. 相似文献
17.
We present the results a study of structure by neutron diffraction and data on the magnetic properties (linear and nonlinear
(second and third order) susceptibilities) of polycrystalline La0.88MnO2.95. This compound exhibits an insulator-metal (IM) phase transition at T
IM
≈ 253 K (above the Curie temperature, T
C
≈ 244 K) and reveals colossal magnetoresistance. The crystal structure is found to be rhombohedral, and the space group is
R3c. Analysis of magnetic properties shows that at T* ≈ 258 K > T
C
, isolated paramagnetic clusters occur in the paramagnetic matrix; their concentration increases upon cooling. We observed
no noticeable differences between the temperature evolution of the clustered state of this manganite with its insulator-metal
transition and in the insulator La0.88MnO2.91. Possible scenarios of the paramagnet-ferromagnet and I-M transitions in a self-organized clustered structure are discussed. 相似文献
18.
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
19.
R. Moubah S. Colis C. Ulhaq-Bouillet G. Schmerber N. Viart M. Drillon A. Dinia D. Muller J. J. Grob 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(3):315-319
Layered cobalt oxides Ca3Co4O9 thin films have been grown directly on c-cut sapphire substrates using pulsed laser deposition. X-ray diffraction and transmission
electron microscopy characterizations show that the deposited films present the expected monoclinic structure and a texture
along the direction perpendicular to the Al2O3(001) plane. The Ca3Co4O9 structure presents six variants in the film plane. Rutherford backscattering spectroscopy shows that the films are stoichiometric
and that the film thickness agrees with the nominal value. The susceptibility χ of the films, recorded along the c-axis of
the substrate, after field cooling and zero field cooling in an applied field of 1 kOe shows two magnetic transitions at 19
and 370 K which agree well with previous findings on single crystal samples. In turn, at low temperature (5 K), the magnetization
curve along the c-axis exhibits coercive field and remanent magnetization much smaller than those reported for bulk samples,
which can be related to the influence of structural variants and structural defects. 相似文献
20.
K. R. Zhdanov M. Yu. Kameneva L. P. Kozeeva A. N. Lavrov 《Physics of the Solid State》2016,58(8):1573-1581
Layered cobaltates YBaCo2O5 + x have been investigated in the oxygen concentration range 0.23 ≤ x ≤ 0.52. It has been revealed that the oxygen ordering plays the key role in the appearance of anomalies in temperature dependences of structural parameters and electron transport. It has been shown that the orthorhombic lattice distortion caused by oxygen chain ordering is a necessary “trigger” for the phase transition from the insulating state to the metallic state at T ≈ 290–295 K, after which the orthorhombic distortion is significantly more pronounced. In the boundary region of the cobaltate compositions, where the oxygen ordering has a partial or local character, there are additional low-temperature (100–240 K) structural and resistive features with a large hysteresis. The observed anomalies can be explained by a change in the spin state of the cobalt ions, which is extremely sensitive to parameters of the crystal field acting on the ions, as well as by the spin-transition-induced delocalization of electrons. 相似文献