共查询到20条相似文献,搜索用时 31 毫秒
1.
N. A. Kalanda G. G. Gorokh M. V. Yarmolich A. A. Lozovenko E. Yu. Kanyukov 《Physics of the Solid State》2016,58(2):351-359
A method has been developed for fabricating nanoporous matrices based on anodic aluminum oxide for the deposition of ferromagnetic nanoparticles in them. The modes of deposition of strontium ferromolybdate thin films prepared by the ion-plasma method have been worked out, and the magnetic and magnetoresistive properties, structure, and composition of the films have been investigated. It has been revealed that the microstructure and properties of the strontium ferromolybdate films deposited by ionplasma sputtering depend on the deposition rate and the temperature of the substrate. Based on the measurement of the electrical resistivity of nanoheterostructures in a magnetic field, it has been found that the magnetoresistance reaches 14% at T = 15 K and B = 8 T, which is due to the manifestation of tunneling magnetoresistance. 相似文献
2.
A. V. Kalgin S. A. Gridnev E. S. Grigorjev 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(9):1097-1100
The inverse magnetoelectric effect and internal friction in two-layer composites based on ferromagnetic Tb0.12Dy0.2Fe0.68 and piezoelectric PbZr0.53Ti0.47O3 are studied in an ac electrical field in the frequency range of 52–213 kHz at temperatures of 293 to 400 K. A correlation is found between the internal friction and the efficiency of the inverse magnetoelectric transformation at resonant frequencies. 相似文献
3.
S. I. Vorob’ev D. S. Andrievskii S. G. Barsov A. L. Getalov E. I. Golovenchits E. N. Komarov S. A. Kotov A. Yu. Mishchenko V. A. Sanina G. V. Shcherbakov 《Journal of Experimental and Theoretical Physics》2016,123(6):1017-1024
A comparative μSR study of ceramic samples of the EuMn2O5 and Eu0.8Ce0.2Mn2O5 multiferroics is performed in the temperature range from 15 to 300 K. It is found that the Ce doping of the EuMn2O5 sample slightly reduces the temperature of the magnetic phase transition from T N = 45 K for the EuMn2O5 sample to T N = 42.5 K for the Eu0.8Ce0.2Mn2O5 sample. Below the temperature T N for both samples, there are two types of localization of a thermalized muon with different temperature dependences of the precession frequency of the magnetic moment of the muon in an internal magnetic field. The higher frequency in both samples refers to the initial antiferromagnetic matrix. The behavior of this frequency in Eu0.8Ce0.2Mn2O5 follows the Curie–Weiss law with the exponent β = 0.29 ± 0.02, which differs from the value β = 0.39 standard for 3D Heisenberg magnetics and is observed in EuMn2O5, because of the strong frustration of the doped sample. The temperature-independent low frequency is due to the presence of Mn3+–Mn4+ ferromagnetic pairs located along the b axis of the antiferromagnetic matrix and in the regions of phase separation, which contain such ion pairs and e g electrons recharging them. In both samples, polarization losses are the same (about 20%) and are associated with the formation of Mn4+–Mn4+ + Mu complexes near Mn3+–Mn4+ ferromagnetic pairs. In the temperature interval from 25 to 45 K, the separation of the Eu0.8Ce0.2Mn2O5 structure into two fractions where the relaxation rates of polarization of muons differ by an order of magnitude is revealed. This effect is due to a change in the state of regions of phase separation (1D superlattices) at the indicated temperatures. Such effect in EuMn2O5 is significantly weaker. 相似文献
4.
L. T. Denisova N. V. Belousova N. A. Galiakhmetova V. M. Denisov E. O. Golubeva 《Physics of the Solid State》2018,60(7):1303-1307
Differential scanning calorimetry has been used to study the influence of temperature on the heat capacity of synthesized vanadates Zn2V2O7, (Cu0.56Zn1.44)V2O7, and (Cu1.0Zn1.0)V2O7. It is found that dependences Cp = f(T) have extremes. The thermodynamic properties of Zn2V2O7 have been determined. 相似文献
5.
6.
R. Nigam A. V. Pan S. X. Dou 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,74(4):429-436
We investigate in detail the dc magnetization and nonlinear ac susceptibility behavior of the superconducting ferromagnet
RuSr2Eu1.5Ce0.5Cu2O10-
δ (Ru1222) to develop a comprehensive understanding of the spin glass and superparamagnetism in this material.
The structural properties of the system result in the formation of magnetic (ferromagnetic) clusters of different sizes, shapes
and properties.
The magnetic clustering of the system leads to observation of various features in dc magnetization and ac susceptibility consistent
with superparamagnetism and cluster spin glass states, which can coexist or stand alone, depending on the temperature range
considered.
Experimental results of magnetic measurements in combination with their analysis have enabled us to explain and distinguish
these phenomena, as well as to propose a temperature dependent scenario of the system behavior. 相似文献
7.
The microwave characteristics of Pb1?x Ca x Fe0.5Nb0.5O3 multiferroics (x = 0.0, 0.4, 0.45, 0.5, 0.55, 0.6), have been investigated as a function of frequency and substitution. The results depict ?13.99 dB reflection loss at 11.65 GHz in composition x = 0.6. Microwave absorption is enhanced with substitution of Ca2+ ions and undoped composition 0.0 behaves as electromagnetic shield. The model governing microwave absorption is discussed and different compositions for electromagnetic applications have been suggested. 相似文献
8.
High field electrical switching on blown films of MoO3(60%)–P2O5(40%), MoO3(50%)–WO3(10%)–P2O5(40%), and MoO3(45%)–WO3(15%)–P2O5(40%) having different thicknesses was studied and compared. Switching was observed using two terminal samples. S-type current–voltage
characteristic (current-controlled negative resistance—CCNR) with memory was observed in molybdenum–phosphate glasses, but
N-type characteristic (voltage-controlled negative resistance—VCNR) with threshold in tungsten–molybdenum–phosphate glasses
was observed. The important observation was that with the addition of WO3 to binary MoO3–P2O5 led to a change of I–V characteristic from CCNR with memory to VCNR with threshold. The measurements of density and molar volume showed linear relation
between MoO3 content and density which decreased with the increase of MoO3 content. The samples’ thickness had no significant effect on threshold voltage. The attained results also indicated that
the electrode material had no effect on switching property of devices. The switching behavior of the devices did not show
any dependence on the polarity of the applied voltage. In terms of the effect of heat on the switching behavior of molybdenum–phosphate
glasses, it was found that threshold voltage decreases with increasing of temperature. Finally, the switching phenomenon was
explained by thermal (formation of crystalline filaments) and electronic models. 相似文献
9.
C. Hess E.M. Ahmed U. Ammerahl A. Revcolevschi B. Büchner 《The European physical journal. Special topics》2010,188(1):103-112
We investigate the transport properties of La1.8−xEu0.2SrxCuO4 (x = 0.04, 0.08, 0.125, 0.15, 0.2) with a special focus on the Nernst effect in the normal state. Various anomalous features
are present in the data. For x = 0.125 and 0.15 a kink-like anomaly is present in the vicinity of the onset of charge stripe order in the LTT phase, suggestive
of enhanced positive quasiparticle Nernst response in the stripe ordered phase. At higher temperature, all doping levels except
x = 0.2 exhibit a further kink anomaly in the LTO phase which cannot unambiguously be related to stripe order. Moreover, a
direct comparison between the Nernst coefficients of stripe ordering La1.8−xEu0.2SrxCuO4 and superconducting La2−xSrxCuO4 at the doping levels x = 0.125 and x = 0.15 reveals only weak differences. Our findings make high demands on any scenario interpreting the Nernst response in
hole-doped cuprates. 相似文献
10.
Jiaming Li Feifei Wang Xiaomei Qin Min Xu Wangzhou Shi 《Applied Physics A: Materials Science & Processing》2011,104(1):117-122
In the present work, (1−x)(0.935Bi0.5Na0.5TiO3–0.065BaTiO3)–xKNbO3 (BNT–BT–KN, BNT–BT–100xKN) ceramics with x ranging from 0 to 0.1 were prepared by the conventional ceramic fabrication process. A large electrostrictive coefficient
of ∼10−2 m4 C−2 is obtained with the composition x ranging from 0.02 to 0.1, which is close to the well-known electrostrictive material Pb(Mg1/3Nb2/3)O3. Under an electric field of 4 kV/mm, the electrostrictive strain can reach as high as 0.08%. Besides, the electric field
induced strain behavior indicates a temperature independent behavior within the temperature range of 20 to 150°C. The large
electrostrictive strain is suggested to be ascribed to the formation of non-polar (NP) phase developed by the KNbO3 substitution, and the high electrostrictive coefficient of BNT–BT–KN ceramics makes them great candidates to be applied in
the new solid-state actuators. 相似文献
11.
A new polyanionic cathode material, Li3V2(PO4)3·LiMn0.33Fe0.67PO4/C for lithium-ion batteries, was synthesized using a sol-gel method and with N,N-dimethyl formamide as a dispersion agent. The analysis of electron transmission spectroscopy and X-ray diffraction revealed that the composite contained two phases. The material has high crystallinity with a grain size of 20–50 nm. The valence states of Mn, V, and Fe in the composite were analyzed by X-ray photoelectron spectroscopy. The electrochemical kinetics in Li3V2(PO4)3 is effectively enhanced by the incorporation of LiMnPO4 and LiFePO4, via structure modification and reduced Li diffusion length. The Li3V2(PO4)3·LiMn0.33Fe0.67PO4/C materials displayed high rate capacity and steady cycle performance with discharge capacity remained 148 mAh g?1 after 50 cycles at the rate of 0.2C. In particular, the composite exhibited excellent reversible capacities, with the values of 157, 134, 120, 102, and 94 mAh g?1 at charge/discharge 0.2, 0.5, 1, 2, and 5C rates, respectively. 相似文献
12.
M. V. Kuznetsov E. V. Shalaeva A. F. Prekul N. I. Shchegolikhina 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(5):628-631
The electronic spectra of the valence band and core levels of the surface of polygrain alloys with the icosahedral structure and the β-(CsCl)-type solid solution of Al50Cu33Fe17 were investigated by X-ray photoelectron spectroscopy (XPS). The obtained XPS spectra of the Al62.5Cu25Fe12.5 alloy, in comparison with those of the crystalline Al50Cu33Fe17 alloy demonstrate narrowing and a decrease in asymmetry of the Fe2p core level and a decrease in the electron state density N(E F ) near the Fermi level, features expected for the poorly conducting icosahedral phase. The XPS data are compared with the estimates of N(E F ) based on the low-temperature specific heat measurements. 相似文献
13.
We investigated influence of bidirectional square wave current with long periods and dc current on the evolution of the voltage-time
(V - t) curves in superconducting polycrystalline bulk Y1Ba2Cu3O7-δ (YBCO) material at the temperatures near the critical temperature. In a well-defined range of amplitudes and periods of driving
current, and temperatures, novel type of non-linear dynamic responses was observed by means of the V-t curves. It was seen
that such a non-linear response to bidirectional square wave current sometimes reflects itself as regular sinusoidal-like
voltage oscillations. The sinusoidal-like and non-sinusoidal oscillations were discussed mainly in terms of the dynamic competition
between pinning and depinning and
significant relaxation effects which appear in this competing process. The density fluctuations associated with the current
induced self-magnetic flux (SMF) lines and semi-elastic coupling of SMF lines with the pinning centers were also considered
as possible physical mechanisms in the interpretation of the experimental results. 相似文献
14.
A series of glasses [(TeO2)
x
(B2O3)1−x
]1−y
[Ag2O]
y
with x = 70 and y = 10, 15, 20, 25 and 30 mol% were synthesised by rapid quenching. Longitudinal and shear ultrasonic velocity were measured
at room temperature and at 5 MHz frequency. Elastic properties, Poisson's ratio, microhardness, softening temperature and
Debye temperature have been calculated from the measured density and ultrasonic velocity at room temperature. The experimental
results indicate that the elastic constants depend upon the composition of the glasses and the role of the Ag2O inside the glass network is discussed. Estimated parameters based on Makishima–Mackenzie theory and bond compression model
were calculated in order to analyse the experimental elastic moduli. Comparison between the experimental elastic moduli data
obtained in the study and the calculated theoretically by the mentioned above models has been discussed. 相似文献
15.
We present strong non-linear dynamic responses developing due to magnitude
and type of driving current in bulk polycrystalline superconducting
Y1Ba2Cu3O7-δ sample at zero magnetic field.
Several novel types of dynamic changes induced by the transport current were
observed via the time evolution of the voltage (V - t curves). The physical
observations appearing in V - t curves were interpreted mainly with the
reorganization of driving current in a multiply connected network of
weak-link structure. It was found that such a dynamic process could cause an
enhancement or suppression in superconducting order parameter due to the
magnitude of the driving current and coupling strength of weak link
structure together with the chemical and anisotropic states of the sample.
It was shown that the general behavior of decays evolving in V - t curves is
consistent with an exponential relation which is analogous to the glassy
state relaxation. 相似文献
16.
Yu. A. Lupitskaya D. A. Kalganov K. V. Abdrakhmanova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2017,11(1):87-91
Features of the formation of lead-ferroniobate compounds in the xBaCO3–(1 – x)PbO–Fe2O3–Nb2O5 system by solid-phase synthesis are investigated. For perovskite-type lead-ferroniobate solid solution, a single-phase concentration region is revealed at 1233 K. The crystalline structures of the synthesized compounds are refined using Rietveld analysis and the Pm3?m and R3m space groups. Ceramic samples of lead ferroniobate are studied by scanning electron microscopy. 相似文献
17.
G. Gritzner J. Ammer K. Kellner V. Kavečanský M. Mihalik S. Maťaš M. Zentková 《Applied Physics A: Materials Science & Processing》2008,90(2):359-365
La0.67Pb0.33(Mn1-xCox)O3-δ ceramics with x=0, 0.01, 0.03, 0.06, 0.1 and 0.15 have been prepared in a two-step procedure. Precursor gels were made by
the wet chemical malic acid method. The gels were calcined and then converted into ceramics by heat treatment at 950 °C and
1000 °C in air. X-ray diffraction showed that the compounds were phase pure. The crystal structure symmetry of the compounds
was confirmed to be rhombohedral (space group R3̄c) for the whole investigated range of x. All compounds undergo a paramagnetic–ferromagnetic
phase transition between 335 K and 225 K. The basic magnetic characteristics such as the Curie temperature , the paramagnetic Curie temperature θ, the effective magnetic moment and the saturated magnetization decrease with increasing Co doping. The ferromagnetic transition is accompanied by an anomaly in the electrical resistance
for all compounds. The high-temperature insulator–metal transitions () do not coincide with the relevant . A large magnetoresistance peak of about 15% was observed for all compounds at .
PACS 72.80.Ga; 75.47.Lx; 75.60.Ej 相似文献
18.
Composite cathode material LiFePO4–Li3V2(PO4)3 is synthesized through a chemical reduction and lithiation using FeVO4·xH2O as both iron and vanadium sources. The structural properties of LiFePO4–Li3V2(PO4)3 are investigated. X-ray diffraction results show the composite material containing olivine type LiFePO4 and monoclinic Li3V2(PO4)3 phases. High-resolution transmission electron microscopy and energy-dispersive X-ray spectrometry results indicate that mutual
doping effects take place between the LiFePO4 and Li3V2(PO4)3 particles with V3+ doping the LiFePO4 while Fe2+ dopes the Li3V2(PO4)3. LiFePO4–Li3V2(PO4)3 nanocomposites are formed in the carbon webs. There is no structural compatibility between monoclinic (Li3V2(PO4)3) and olivine (LiFePO4) domains in composite material LiFePO4–Li3V2(PO4)3. 相似文献
19.
Organic–inorganic hybrid sample [N(C4H9)4]2Cu2Cl6 was prepared via the reaction between copper chloride and tetrabutylammonium chloride. The compound was characterized by
X-ray powder diffraction, IR, Raman, differential scanning calorimetry (DSC), DTA-TGA analysis and electrical impedance spectroscopy.
DSC studies indicate a presence of one-phase transition at 343 K. The complex impedance of compound [N(C4H9)4]2Cu2Cl6 have been investigated in temperature and frequency ranges 300–380 K and 200 Hz–5 MHz, respectively. The Z′ and Z″ versus frequency plots are well fitted to an equivalent circuit model. The circuits consist of the parallel combination
of bulk resistance R
p and constant phase elements CPE. The frequency dependence of the conductivity is interpreted in term of Jonscher's law: s(w) = sdc + Awn \sigma (\omega ){ } = {\sigma_{\rm{dc}}} + { }A{\omega^n} . The conductivity follows the Arrhenius relation. The variation of the value of these elements with temperatures confirmed
the availability of the phase transition at 343 K detected by DSC and electrical measurements. 相似文献
20.
G.?Urbanik T.?H?nke C.?Hess B.?Büchner A.?Ciszewski V.?Hinkov C. T.?Lin B.?Keimer 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(4):483-489
We performed scanning tunneling microscopy and spectroscopy on untwinned crystals of underdoped YBa2Cu3O7-
δ at δ = 0.4. A comprehensive statistical analysis of our topographic data indicates a doping dependent cleaving behavior of
this material. We find in particular that at δ = 0.4 the material primarily cleaves in multiples of one unit cell along the
c-axis with a high corrugation of the topmost layer. Our data suggest that the low temperature cleaving mainly results in
a disruption of the CuO chain layers involving a redistribution of the layer atoms onto the two cleaving planes. In a few instances, fractional
step heights (in terms of the c-axis lattice constant) are observed as well. Scanning tunneling spectroscopy reveals that
such fractional steps connect surfaces which differ significantly in their tunneling conductance. 相似文献