共查询到20条相似文献,搜索用时 31 毫秒
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.
S. S. Pawar K. P. Shinde R. S. Joshi R. S. Kalubarme A. G. Bhosale S. H. Pawar 《Ionics》2010,16(7):649-654
Nano-crystalline films of Sm0.5Sr0.5CoO3 (SSC) have been formed on CeO2 substrates by spraying stoichiometric aqueous solution containing Sm, Sr, and Co ions. Effect of polyvinyl alcohol (PVA)
addition as a complexing agent in spray solution on stoichiometry, crystallite size, morphology, and transport properties
of film are studied. The results showed that the SSC cathode had maximum crystallite size for 40% PVA addition. Electrical
performance of film decreases with decrease in the particle size, while the electronic to ionic predominance transition temperature
decreases with decreasing particle size. These films are studied for their potential application as a cathodic material in
developing intermediate temperature solid oxide fuel cells. 相似文献
3.
S. B. Erenburg S. V. Trubina K. O. Kvashnina V. N. Kruchinin V. V. Gritsenko A. G. Chernikova A. M. Markeev 《Journal of Experimental and Theoretical Physics》2018,126(6):816-824
The microstructures of amorphous and polycrystalline ferroelectric Hf0.5Zr0.5O2 films are studied by X-ray spectroscopy and ellipsometry. EXAFS spectra demonstrate that the amorphous film consists of an “incompletely mixed” solid solution of metallic oxides HfO2 and ZrO2. After rapid thermal annealing, the mixed Hf0.5Zr0.5O2 oxide films have a more ordered polycrystalline structure, and individual Hf and Zr monoxide islands are formed in the films. These islands are several nanometers in size and have a structure that is similar to the monoclinic structure of HfO2 and ZrO2. The presence of the HfO2 and ZrO2 phases in the Hf0.5Zr0.5O2 films is also detected by ellipsometry. 相似文献
4.
G. A. Ovsyannikov A. M. Petrzhik I. V. Borisenko A. A. Klimov Yu. A. Ignatov V. V. Demidov S. A. Nikitov 《Journal of Experimental and Theoretical Physics》2009,108(1):48-55
The electrical and magnetic characteristics of La0.7Sr0.3MnO3 (LSMO) epitaxial manganite films are investigated by different methods under conditions when the crystal structure is strongly strained as a result of mismatch between the lattice parameters of the LSMO crystal and the substrate. Substrates with lattice parameters larger and smaller than the nominal lattice parameter of the LSMO crystal are used in experiments. It is shown that the behavior of the temperature dependence of the electrical resistance for the films in the low-temperature range does not depend on the strain of the film and agrees well with the results obtained from the calculations with allowance made for the interaction of electrons with magnetic excitations in the framework of the double-exchange model for systems with strongly correlated electronic states. Investigations of the magneto- optical Kerr effect have revealed that an insignificant (0.3%) orthorhombic distortion of the cubic lattice in the plane of the NdGaO3(110) substrate leads to uniaxial anisotropy of the magnetization of the film, with the easy-magnetization axis lying in the substrate plane. However, LSMO films on substrates (((LaAlO3)0.3+(Sr2AlTaO6)0.7)(001)) ensuring minimum strain of the films exhibit a biaxial anisotropy typical of cubic crystals. The study of the ferromagnetic resonance lines at a frequency of 9.76 GHz confirms the results of magnetooptical investigations and indicates that the ferromagnetic phase in the LSMO films is weakly inhomogeneous. 相似文献
5.
Compressed
Pr0.5Ca0.5MnO3
films (250 nm) deposited on LaAlO3 have
been studied by Electron Spin Resonance technique under high
frequency and high magnetic field. We show evidences for the
presence of a ferromagnetic phase (FM) embedded in the
charge-order phase (CO), in form of thin layers which size
depends on the strength and orientation of the magnetic field
(parallel or perpendicular to the substrate plane). This FM
phase presents an easy plane magnetic anisotropy with an
anisotropy constant 100 times bigger than typical bulk values.
When the magnetic field is applied perpendicular to the
substrate plane, the FM phase is strongly coupled to the CO
phase whereas for the parallel orientation it keeps an
independent ferromagnetic resonance even when the CO phase
becomes antiferromagnetic. 相似文献
6.
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
7.
M. Belmeguenai S. Mercone C. Adamo T. Chauveau L. Méchin P. Monod P. Moch D. G. Schlom 《Journal of nanoparticle research》2011,13(11):5669-5675
Nearly 50-nm thick La0.7Sr0.3MnO3 (LSMO) films were grown on Si substrates using molecular beam epitaxy on (001) Si substrates over-layered by a 20 nm thick
SrTiO3 (STO) or by a 20 nm thick CaTiO3 (CTO) film. In addition, a reference LSMO film was directly deposited on a (001) STO substrate by pulsed laser deposition.
For all the samples, X-ray diffraction revealed an excellent epitaxy of the LSMO film and small mosaicity around (001), with
in-plane [100] and [010] cubic axes. The LSMO/CTO films are in-plane compressed while the LSMO/STO ones are in-plane extended.
The temperature dependence of their static magnetic properties was studied using a SQUID, showing a Curie temperature overpassing
315 K for all the samples. Hysteresis loops performed at room temperature (294 K) with the help of a vibrating sample magnetometer
(VSM) are also discussed. At 294 K Micro-strip ferromagnetic resonance (MS-FMR) was used to investigate the dynamic magnetic
properties. It allows concluding to a strong anisotropy perpendicular to the films and to a weak fourfold in-plane anisotropy
with easy axes along the [110] and [1[`1]0 1\bar{1}0 ] directions. Their values strongly depend on the studied sample and are presumably related to the strains suffered by the
films. 相似文献
8.
A. N. Veis 《Russian Physics Journal》2008,51(7):714-717
Spectra of optical absorption in Bi0.5Sb1.5Te3 films grown on mica and KBr substrates have been investigated for T = 145 and 300 K. The data obtained have been analyzed
together with the data of investigations on the fundamental absorption edge for Bi2Te3 available in the scientific literature. It has been revealed that the interband absorption spectra for both Bi0.5Sb1.5Te3 and Bi2Te3 represent a superposition of two components corresponding to direct and indirect allowed optical transitions. In this case,
the least energy gap separating the valence band and the conduction band is direct for Bi2−xSbxTe3 (x ≤ 1.5, T = 300 K). For Bi0.5Sb1.5Te3 the temperature variation rates have been estimated for the thresholds of direct and indirect interband transitions. It has
been shown that this solid solution is direct gap solution at T ≥ 145 K.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 50–52, July, 2008. 相似文献
9.
The atomic and magnetic structures of La0.5Ca0.5CoO3 cobaltite have been studied by the neutron diffraction technique at high pressures of up to 4 GPa in the 10- to 300-K temperature
range. The pressure dependences of the structural parameters have been obtained. The Curie temperature increases with the
pressure with the coefficient dT
C/dP = 1 K/GPa, demonstrating the stability of the ground ferromagnetic (FM) state. The pressure dependence of the ground FM state
in La0.5Ca0.5CoO3 is in drastic contrast with that for La1 − x
Ca
x
CoO3 at a lower calcium content (x < 0.3). For the latter compound, the pressure suppressed the ground FM state and a large negative pressure coefficient of
the Curie temperature (dT
C/dP ∼ −10 K/GPa) was observed. The nature of such a phenomenon is analyzed in the framework of the double exchange model also
taking into account the changes in the electron configuration of Co3+ ions. 相似文献
10.
The crystal structure and magnetic properties of the (La0.3Sr0.7)0.5Ca0.5FeO3 solid solution with a perovskite structure have been investigated. The solid solution has been synthesized according to the
high-pressure technique. The unit cell parameters have been refined using the Rietveld full-profile analysis under the assumption
of the single-phase crystalline state and the two-phase model corresponding to the parent compositions. It follows from the
calculations that the best agreement between the experimental data and the theoretical curve is observed for the two-phase
model. The measurement of the magnetic properties also indicates the coexistence of two magnetic phases. 相似文献
11.
The structure and dielectric characteristics of the (1000 nm)SrTiO3 spacer in a (001)SrRuO3 ‖ (001)SrTiO3 ‖ (001)La0.67Ca0.33MnO3 trilayer heterostructure grown on a (001)(LaAlO3)0.3+(Sr2AlTaO6)0.7 substrate have been studied. Both oxide electrodes, as well as the strontium titanate layer, were cube-on-cube epitaxially grown. The unit cell parameter in the SrTiO3 layer measured in the substrate plane (3.908±0.003 Å) practically coincided with that determined along the normal to the substrate surface (3.909±0.003 Å). The temperature dependence of the real part of the permittivity ?′ of the SrTiO3 layer in the range 70–180 K fits the relation (?′)?1 ~ ? 0 ?1 C 0 ?1 (T-T C ) well, where C0 and TC are the Curie constant and the Curie-Weiss temperature, respectively, for bulk strontium titanate crystals and ?0 is the free-space permittivity. The data obtained on the temperature dependence of the permittivity of SrTiO3 films enabled us to evaluate the effective depth of electric field penetration into the manganite electrode (L e ≈ 0.5 nm) and the corresponding capacitance (C e ≈1×10?6 F/cm2) of the interface separating the (001)SrTiO3 layer from the (001)La0.67Ca0.33MnO3 bottom electrode. 相似文献
12.
A. Geddo Lehmann C. Sanna N. Lampis F. Congiu G. Concas L. Maritato C. Aruta A. Yu. Petrov 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(4):337-345
Thin films of La0.7Sr0.3MnO3 were grown by
molecular beam epitaxy on (001)LaAlO3 crystals. High resolution X-ray
diffraction analysis proves the presence of twins in the films at room
temperature, showing that the twin structure of the substrate which forms at
the
ferroelastic transition at TF = 813 K
served as a template for the film microstructure. Magnetic measurements
indicate a thermomagnetic irreversibility which is ascribed to the quenched
disorder related to twinning and discussed in terms of coexisting
ferromagnetic and spin disordered regions connected with the undeformed
domain cores and strained domain walls respectively. 相似文献
13.
The electronic structure of stoichiometric and oxygen-depleted Hf0.5Zr0.5O2 in the orthorhombic noncentrosymmetric phase has been studied by X-ray photoelectron spectroscopy and quantum-chemical simulation based on the density functional theory. It has been established that the ion-etching-induced peak in the photoelectron emission spectrum with the energy above the top of the o-Hf0.5Zr0.5O2 valence band is due to oxygen vacancies. A method of estimating the density of oxygen vacancies from the comparison of the experimental and theoretical photoelectron spectra of the valence band has been proposed. It has been established that oxygen polyvacancies in o-Hf0.5Zr0.5O2 are not formed: the energetically favorable spatial arrangement of oxygen vacancies in a crystal corresponds to noninteracting oxygen vacancies distant from each other. 相似文献
14.
X.T. Li P.Y. Du H. Ye C.L. Mak K.H. Wong 《Applied Physics A: Materials Science & Processing》2008,92(2):397-400
Textured LixNi2-xO (LNO) thin films have been fabricated on (001)MgO substrates by pulsed laser deposition technique. The as-deposited LNO
films shows a conductivity of 2.5×10-3 Ω m and possess a transmittance of about 35% in the visible region. Subsequent deposition of Sr0.6Ba0.4Nb2O6 (SBN60) thin film on these LNO-coated MgO substrates resulted in a textured SBN layer with a 〈001〉 orientation perpendicular
to the substrate plane. Phi scans on the (221) plane of the SBN layer indicated that the films have two in-plane orientations
with respect to the substrate. The SBN unit cells were rotated in the plane of the film by ± 8.2° as well as ± 45° with respect
to the LNO/MgO substrate. Besides the highly (00l)-orientation, the SBN films also exhibited a dense microstructure as shown
by scanning electron microscopy. The electro-optic coefficient (r33) of the SBN film was measured to be 186 pm/V. On the basis of our results, we have demonstrated that the LNO film can be
used as a buffer layer as well as a transparent bottom electrode for waveguide applications. The SBN/LNO heterostructure is
also a suitable candidate for integrated electro-optics devices.
PACS 42.79.Gn; 42.82.Et; 78.20.Ci 相似文献
15.
The Rb3(HSeO4)2.5(H2PO4)0.5 compound was prepared and its thermal behavior and electric properties were investigated. The thermogravimetry (TGA) analysis and the differential scanning calorimetric (DSC) show the presence of a structural phase transition of the title compounds at 374 K which is confirmed by the variation of fp and σdc as a function of temperature. The complex impedance of the Rb3(HSeO4)2.5(H2PO4)0.5 compound has been investigated in the temperature range of 295–453 K and in the frequency range 209 Hz–1 MHz. The impedance plots show semicircle arcs at different temperatures, and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance Rp and constant phase elements CPE1 in series with fractal capacity CPE2. The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law. The conductivity dc follows the Arrhenius relation. The near value of activation energies obtained from the analysis of modulus, conductivity data, and circuit equivalent confirm that the transport is through the ion hopping mechanism, dominated by the motion of the H+ proton in the structure of the investigated materials. 相似文献
16.
Single-crystal (100) and (001) TiO2 rutile substrates have been implanted with 40 keV Fe+ at room temperature with high doses in the range of (0.5–1.5) × 1017 ions/cm2. A ferromagnetic resonance (FMR) signal has been observed for all samples with the intensity and the out-of-plane anisotropy increasing with the implantation dose. The FMR signal has been related to the formation of a percolated metal layer consisting of close-packed iron nanoparticles in the implanted region of TiO2 substrate. Electron spin resonance (ESR) signal of paramagnetic Fe3+ ions substituting Ti4+ positions in the TiO2 rutile structure has been also observed. The dependences of FMR resonance fields on the DC magnetic field orientation reveal a strong in-plane anisotropy for both (100) and (001) substrate planes. An origin of the in-plane anisotropy of FMR signal is attributed to the textured growth of the iron nanoparticles. As result of the nanoparticle growth aligned with respect to the structure of the rutile host, the in-plane magnetic anisotropy of the samples reflects the symmetry of the crystal structure of the TiO2 substrates. Crystallographic directions of the preferential growth of iron nanoparticles have been determined by computer modeling of anisotropic ESR signal of substitutional Fe3+ ions. 相似文献
17.
A. M. Balagurov I. A. Bobrikov V. Yu. Pomjakushin E. V. Pomjakushina D. V. Sheptyakov I. O. Troyanchuk 《JETP Letters》2011,93(5):263-268
The magnetic and crystal structures of the Pr0.5Sr0.5CoO3 metallic ferromagnet have been studied by the neutron diffraction technique. It is demonstrated that below 150 K, the compound
is mesoscopically separated into two crystalline phases with different spatial symmetries and with different directions of
the magnetic anisotropy. The phase separation exists down to 1.5 K, and at temperatures below 90 K, the low-symmetry phase
occupies about 80% of the sample volume. The main structural difference between the phases is the configuration of oxygen
atoms around praseodymium and, to a certain extent, around cobalt. The ferromagnetic structure with the magnetic moment lying
in the basal plane of the structure (μCo ≈ 1.7 μ
B
at 1.5 K) arises at 234 K, whereas the component directed along the long axis of the unit cell appears at 130 K. The formation
of the new structural phase and change in the orientation of the magnetic moment give rise to the anomalies of the physical
and magnetic characteristics of this compound observed earlier at temperatures about 120 K. 相似文献
18.
N. A. Babushkina A. Maignan A. N. Taldenkov A. V. Inyushkin E. A. Chistotina 《Journal of Experimental and Theoretical Physics》2007,105(1):112-115
The effect of oxygen isotope substitution on the properties of Pr0.5Ca0.5Mn1 ? x Cr x O3 manganites (x = 0, 0.02, 0.05) have been studied. The introduction of chromium favors (i) the decomposition of a charge-ordered state and (ii) the appearance of a ferromagnetic metallic phase in Pr0.5Ca0.5Mn1 ? x Cr x 16–18O3. The isotope substitution 16O → 18O leads to a decrease in the content of the ferromagnetic phase, an increase in the charge-ordering transition temperature (T CO), and a decrease in the ferromagnetic transition temperature (T FM). The isotope mass exponent is evaluated. 相似文献
19.
G. A. Komandin V. I. Torgashev A. A. Volkov O. E. Porodinkov I. E. Spektor V. M. Mukhortov 《Physics of the Solid State》2010,52(9):1842-1849
Transmission and reflection spectra of Bi0.98Nd0.02FeO3.00 multiferroic thin films on MgO single-crystal substrates have been measured using submillimeter spectroscopy (on a backward-wave
tube spectrometer) and Fourier-transform infrared spectroscopy in the frequency range from 8 to 1000 cm−1 at room temperature. The complex permittivity spectra of the films have been calculated in terms of the layered medium model.
It has been revealed that a decrease in the film thickness leads to a considerable increase in the losses in a range of 30
cm−1 and the corresponding fivefold increase in the static permittivity (to 500 for a film 32 nm thick). This phenomenon has been
discussed in the framework of the phenomenological theory of phase transitions. 相似文献
20.
Based on Landau-Devonshire (LD)-type phenomenological
thermodynamic theory, the electric field dependence of the
dielectric properties of tetragonal single-domain barium strontium
titanate(Ba1-xSrxTiO3) films on cubic substrates is
theoretically investigated by taking into account the high order
terms of the polarization. At room temperature, the nonlinear
dielectric responses of epitaxial Ba0.6Sr0.4TiO3
films are provided by adjusting the film thickness and growth
temperature. The strong nonlinearity of relative dielectric
constant and pyroelectric coefficient are attained around critical
film thickness on MgO (69 nm) and LaAlO3 (132 nm) substrates or
critical growth temperature on MgO (337 °C) substrate with
respect to epitaxy-induced lattice misfit and thermal stresses
during deposition. This can be explained that small compressive
stresses are effective to support high nonlinearity of dielectric
constant and pyroelectric coefficient for
Ba0.6Sr0.4TiO3 films irrespective of whether they are
on compressive substrate or tensile substrate. It is also
predicted that a large tunability may be achieved by altering
processing conditions, such as the film thickness and growth
temperature for different substrates.
Our theoretical results are in good agreement with the experimental data reported in literature. 相似文献