共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Oyasato K. Ichinose K. Fujiwara A. Tsujimura 《Journal of magnetism and magnetic materials》1987,70(1-3):233-235
The spin echo spectra of 89Y hyperfine fields in Y(Fe1−xTx)3 with low concentration x consist of two main lines and of satellite lines caused by the replacement of the Fe atoms by the T atoms. Values of the magnetic moments of the T atoms are estimated by observing the satellite lines. 相似文献
2.
T. Sakakibara T. Goto K. Yoshimura M. Shiga Y. Nakamura K. Fukamichi 《Journal of magnetism and magnetic materials》1987,70(1-3):126-128
Magnetization measurements have been carried out on the Laves phase compounds M(Co1−xAlx)2(M = Y, Lu) up to 42 T. Sharp metamagnetic transitions with small hysteresis are found in Y(Co1−xAlx)2, while broad transitions with large hysteresis are found in Lu(Co1−xAlx)2. The results suggest that the former compounds are magnetically homogeneous but the latter inhomogenous. 相似文献
3.
Y. Andoh T. Hashimoto H. Fujii T. Okamoto H. Fujiwara 《Journal of magnetism and magnetic materials》1987,70(1-3):168-170
Measurements of magnetization and 57Fe Mössbauer spectra have been made for Y(Fe1−xRux)2. The C15 type cubic structure is stabilized for x0.06 and the C14 type hexagonal structure for x 0.7. The C15 compounds is ferromagnetic with Tc200 K and its saturation moment decreases monotonically with increasing x, while the 57Fe hyperfine field decreases only slightly with x. From these results, it is deduced that the Ru atoms have an induced moment of ≈1μB in the range x 0.2. In the C14 type phase, no magnetic ordering develops even at 4.2 K. 相似文献
4.
K. Ichinose K. Fujiwara M. Nakamura M. Oyasato A. Tsujimura 《Journal of magnetism and magnetic materials》1987,70(1-3):154-156
Nuclear magnetic resonances of 59Co nuclei in (Mg1−xRx)Co2 (R = Y, Gd) compounds at 4.2 K have been observed for 0x1. By replacing Mg with R, the 59Co hyperfine field decreases or is nearly constant in the C14 range and increases in the C15 range. These results are explained by the difference of the contribution from R atoms. 相似文献
5.
New Scheelite-related solid solutions of the compositions Nax/2Bi1−x/2MoxV1−xO4 (0≤x≤1) and Bi1−x/3 MoxV1−xO4(0≤x≤0.2) have been synthesised by the substitution of Na and Mo at the A and B sites respectively of the ABO4 type ferroelastic BiVO4. The phases were characterised using chemical analysis, powder X-ray diffraction, scanning electron microscopy, EDAX, and Raman spectroscopy. While almost a continuous solid solution is obtained for the series Nax/2Bi1−x/2MoxV1−xO4, the absence of Na at the A-site results only in a narrow stability region for the other series, Bi1−x/3 MoxV1−xO4 where 0≤x≤0.2. Raman spectra of selected samples at room temperature also suggest that vanadium and molybdenum atoms are disordered at the tetrahedral sites. 相似文献
6.
A 27Al nuclear magnetic resonance (NMR) investigation at room temperature of the Pb1 − xAlxF2 + x (0 ≤ x ≤ 0.12) solid solution and of the ordered Pb9Al2F24 phase is carried out. Two different types of aluminium ions are identified and their ratio is determined as a function of x. A clustering process based on the formation of column clusters, more and more extended when x increases, is proposed on the basis of results issued from the 19F (Part I) and 27Al NMR investigations. 相似文献
7.
Z. Tomkowicz 《Physica C: Superconductivity and its Applications》1999,320(3-4):173-182
Pr concentration dependence of the superconducting transition temperature Tc in the Ho1−xPrxBa2Cu3O7−δ system is determined from measurements of DC electrical resistance. This dependence coincides with that for the parallely studied Y1−xPrxBa2Cu3O7−δ reference system. Both systems have the same value of the critical concentration xc=0.58, in accordance with nearly equal ionic radii of Ho3+ and Y3+ ions. It has been shown that the Tc(x) curve can be described with a single mechanism based on a decreasing number of sheet holes trapped by PrIV-ions, if one takes also into account that the number of these ions changes with x. 相似文献
8.
Hiroyuki Shibata Kyoichi Kinoshita Tomoaki Yamada 《Physica C: Superconductivity and its Applications》1990,170(5-6):411-415
Superconductivity and crystallographic properties of La2 − xMxCuO4 − δ (M = Na, K) are studied. In the La2 − xMxCuO4 − δ system, superconductivity is detected for x 0.2. Oxygen content analysis shows that the system has more oxygen vacancies than the La2 − xSrxCuO4 − δ system. These oxygen vacancies may reduce the hole concentration, and high Na-doping is needed to produce superconductivity. In the La2 − xKxCuO4 − δ system, superconductivity is observed for the first time. Resistivity and magnetic susceptibility measurements show that Tc(onset) is 40 K and the Meissner volume fraction is about 4% for x = 0.7. The system changes from orthorhombic to a tetragonal K2NiF4 structure at x ≈ 0.3 and only tetragonal samples show superconductivity. 相似文献
9.
Tracer diffusion of 18O in dense, polycrystalline La1−xSrxCoO3 for x = 0.1 has been measured in the temperature range 400 to 600 °C and at 500 °C for x = 0.2 at an oxygen partial pressure of 1 × 105 Pa. Depth profiles were obtained by secondary ion mass spectrometry. The diffusion coefficient for La0.9Sr0.1CoO3 is given by D = (17–247) exp[(−232 ± 8 kJ/mole)/RT] cm2/s. This value is several orders of magnitude lower than D extrapolated from the results for x = 0.2 measured in the 700–900 °C temperature range. One possible explanation for the discrepancy is that the two measurements reflect different diffusion paths. As expected, La0.8Sr0.2CoO3 exhibits a higher diffusivity at 500 °C than does La0.9Sr0.1CoO3. 相似文献
10.
Akira Ono 《Physica C: Superconductivity and its Applications》1992,200(3-4):296-300
The compounds Ba1.4Sr0.6YCu3Oz (7.0≤z<7.4) were synthesized at 2 GPa to clarify the effect of high temperature and pressure on the superconducting properties. The structure as observed by powder X-ray diffraction was tetragonal for z≥7.2, and orthorhombic or tetragonal for z<7.1. It has been revealed that high-pressure syntheses suppress the superconductivity in the compounds with z<7.1. Recovery of the superconducting properties occurs above z≥7.2. The effect of Sr substitution on the superconducting properties was also studied. The magnitude of diamagnetism at 5–30 K decreases monotonically from −0.003 to −0.0002 emu/g Oe with increasing x in Ba2−xSrxYCu3Oz (x≥1.2). 相似文献
11.
A 19F-NMR investigation of the Pb1 − xAlxF2 + x (0 ≤ x ≤ 0.12) solid solution and of the ordered Pb9Al2F24 phase is undertaken as a function of temperature. Several F− ion groups become progressively mobile at the NMR time scale at increasing temperature, the first, (Fi)pb and (Fn)pb, are located in the surroundings of Pb2+ cations, the second ones, (Frd)AI and (Fra)Al, in that of Al3+ cations. Four types of fluoride ions are distinguished in the 19F-NMR spectra of rigid lattice at low temperature (T = 175 K) and the distribution of fluoride ions among the four sites is determined by deconvolution of the spectra registered. The sites occupied by the (Fn)pb anions are identified with the normal anionic sites of the fluorite network, the others with different interstitial sites. 相似文献
12.
Serial single-phase Gd2(Fe1−x−yCoyTix)17 compounds have been synthesized. These compounds have a crystal structure belonging to rhombohedral lattice with
space group. The lattice parameters of compounds decrease with cobalt content and increase with titanium content, respectively. The saturation magnetization decreases with increasing cobalt and titanium contents. The anisotropy fields increase to maximum then decrease with cobalt concentration. The magnetocrystalline anisotropy constants increase with cobalt content from negative to positive maximum and then decrease with Co concentration. The saturation moment of the compounds decreases linearly with cobalt concentration and decreases nonlinearly with titanium concentration. 相似文献
13.
P.E. Kazin V.V. Poltavets Y.D. Tretyakov M. Jansen B. Freitag W. Mader 《Physica C: Superconductivity and its Applications》1997,280(4):31-265
Phase evolution in the Bi---Sr---Ca---Cu---Al---O system was studied. Two Al-containing phases BiSr1.5Ca0.5Al2Oz and (Sr1−xCax)3Al2O6 (x = 0.4 − 0.45) were determined to be chemically compatible with Bi2.18Sr2CaCu2O8+x (Bi-2212) at temperatures of the samples processing. The phase equilibria in the title system were investigated above the solidus temperature. The BiSr1.5Ca0.5Al2Oz was found to be in equilibrium only with the melt and the (Sr1−xCax)3Al2O6 phase. This latter aluminate equilibrated with Ca,Sr cuprates, CaO, the Cu-free phase, and the liquid. The melting and solidification in Bi-2212, doped with the aluminate, corresponded to the reversible reaction Bi-2212 + BiSr1.5Ca0.5Al2Oz ↔ (Sr1−xCax)3Al2O6 + liquid. Two sets of superconducting composite materials with initial compositions Bi-2212 + nBiSr1.5Ca0.5Al2Oz and Bi-2212 + m(Sr1−xCax)3Al2O6 were prepared by solidification from the partial melt. The former material was composed mostly of large Bi-2212 lamellas separated by the BiSr1.5Ca0.5Al2Oz phase, which destroyed superconducting links between Bi-2212 grains. The latter material consisted of a Bi-2212 polycrystalline matrix with high concentration of small (ca. 3 μm) grains of (Sr1−xCax)3Al2O6 imbedded in Bi-2212 lamellas. The Bi-2212 + m(Sr1−xCax)3Al2O6 materials displayed a trend to enhance flux pinning at T = 60 K with the increase of aluminate phase content. 相似文献
14.
N. Watanabe K. Kuroda K. Abe N. Koshizuka M. Tagami Y. Shiohara 《Physica C: Superconductivity and its Applications》1998,300(3-4):301-308
The polarized Raman spectra of Nd1+xBa2−xCu3O7−δ (−0.023≤x≤0.107) and Pr1+xBa2−xCu3O7−δ (0.01≤x≤0.15) single crystals have been investigated. It was found that the Cu(2) Ag mode softens by 6 cm−1 in Nd 1:2:3 and 4 cm−1 in Pr 1:2:3 as x increases. These frequency shifts cannot be explained by the change in the relevant bond lengths due to Nd(Pr)-substitution for Ba. The variations with x of the two low frequency modes may be affected by change of their hybridization and/or change of their force constants. The linewidths of Ba mode in Pr 1:2:3 are broader than those in Y 1:2:3. This result suggests that the Pr substitution on Ba sites occurred even in a very small value of x. In x(yy)
geometry the relative intensity of the Ba and O(4) modes in Nd 1:2:3 is greater than those in Pr 1:2:3. The difference between Nd 1:2:3 and Pr 1:2:3 in the relative intensity of the Ba and O(4) modes may be produced by the chains. 相似文献
15.
M. S. Han T. W. Kang M. D. Kim Y. T. Jeoung H. K. Kim J. M. Kim H. J. Woo T. W. Kim 《Applied Surface Science》1997,120(3-4):287-290
Fourier transform infrared (FTIR) transmission, Hall effect, and nuclear resonance reaction measurements have been carried out to investigate the effect of hydrogenation on the deep levels and the hydrogen depth profiling in nominally undoped HgxCd1 − xTe layers grown on undoped p-CdTe (211) B-orientation substrates by molecular beam epitaxy. After hydrogenation, the FTIR spectra showed that the transmittance intensity increased in comparison to that of the as-grown HgxCd1 − xTe and that the absorption edge shifted to the short wavelength range. Hall effect measurements showed that the carrier concentration decreased and the mobility increased after hydrogenation. After hydrogenation, p-type HgxCd1 − xTe is converted to n-type HgxCd1 − xTe with high resistivity. Nuclear resonance raaction measurements show that the concentration and the penetration depth of the hydrogen atom in n-Hg0.77Cd0.23Te are 3.5% and 640 Å, respectively. The areal density of the hydrogen-containing layer at the surface of the hydrogenated n-Hg0.77Cd0.23Te film is 4.39 × 1015 atoms/cm2. These results indicate that hydrogen atoms not only effectively passivate impurities or defects in the HgxCd1 − xTe film but also change the carrier type of p-HgxCd1 − xTe. 相似文献
16.
C. Jeandey J. L. Oddou
B. Boucher
R. TourbotG. Czjzek
《Journal of magnetism and magnetic materials》1990,89(3):335-349Magnetic interactions and effects of dilution with nonmagnetic Y on the magnetic properties of crystalline and amorphous alloys GdxY50−xAg50 (10 ≤ x ≤ 50) have been investigated by measurements of bulk magnetization and susceptibility and by Mössbauer spectroscopy with 155Gd. The crystalline alloys order antiferromagnetically for all Gd concentrations with a noncollinear arrangement of Gd moments induced by negative biquadratic exchange interactions. In amorphous alloys, ferromagnetic order is found for large Gd concentrations (x ≥ 40). Below the critical concentration xcr, in the range 30<xcr<40, properties typical for magnetic cluster glasses are observed. Magnetic hyperfine fields Bhf at 155Gd nuclei vary with x in opposite directions in amorphous and in crystalline alloys. In crystalline alloys, the variation is due to a positive transferred hyperfine field. In amorphous alloys, a reduction of |Bhf| with decreasing Gd concentration is caused by a reduction of the frozen Gd moments in the cluster glass phase. 相似文献
17.
In order to understand the mechanism that gives rise to superconductivity in the ceramic superconductors of the type BaxK1 − xBiO3, we analyze the thermodynamic properties with the use of the Eliashberg equations. For these calculations we used the electron-phonon spectral density function 2(ω)F(ω), calculated by Shirai et al. [1] from first principles for two different K concentrations, x=0.5 and x=0.7. 相似文献
18.
A. Novosselov A. Yoshikawa M. Nikl N. Solovieva J. -H. Lee T. Fukuda 《Radiation measurements》2004,38(4-6):481-483
Shaped single crystals of (LuxGd1−x)3Ga5O12 (0.0x1.0) and (Yb0.05LuxGd0.95−x)3Ga5O12 (0.0x0.9) were grown by the modified micro-pulling-down method. Continuous solid solutions with garnet structure and a linear compositional dependency of crystal lattice parameter in the system Yb:(Gd,Lu)3Ga5O12 are formed. Measured optical absorption spectra of the samples show 4f–4f transitions related to Gd3+ ion at 275 and 310 nm, and also an onset of charge transfer transitions from oxygen ligands to Gd3+ or Yb3+ cations below 240 nm. A complete absence of Yb3+ charge transfer luminescence under X-ray excitation in any of the investigated samples was explained by the overlapping of charge transfer absorption of Yb3+ by that of Gd3+ ions. For specific composition of Lu1.5Gd1.5Ga5O12 an intense defect-host lattice-related emission, which achieve of about 40% integrated intensity compared with Bi4Ge3O12, was found. 相似文献
19.
Y. Yamada Y. Kitaoka K. Asayama A. Sakata 《Journal of magnetism and magnetic materials》1987,70(1-3):175-177
The magnetic phase diagram has been investigated in the C14 type (Zr1−xNbx)Fe2 with x0.7 from 93Nb NMR and magnetization measurements. In the compound with x = 0.825 a first order-like transition has been found to occur around 25 K from a canted state with the ferromagnetic moment in the basal plane to a ferromagnetic state with decreasing temperature. 相似文献
20.
A. T. Naveed M. Q. Huda K. F. Abd El-Rahman J. Hartung J. H. Evans-Freeman A. R. Peaker D. C. Houghton C. Jeynes W. P. Gillin 《Journal of luminescence》1998,80(1-4):381-386
Strained Si1−xGex/Si quantum wells have been doped with erbium by implantation. A comparison is made with strained Si1−xGex/Si quantum wells and relaxed Si1−xGex, with x between 10% and 25%, doped with erbium during MBE growth. The erbium concentration was between 1×1018 and 5×1018 cm−3 throughout the active regions. Transmission electron microscopy, X-ray diffraction, and photoluminescence studies indicate that good regrowth can been achieved after full amorphisation by implantation of the strained quantum wells. The erbium luminescence is more intense in the Si1−xGex/Si layers, but erbium-implanted samples containing Si1−xGex exhibit defect luminescence in the region of 0.9–1.0 eV. These defects are also present when Si1−xGex/Si quantum wells are implanted with an amorphising dose of silicon, and then regrown. They are attributed to small germanium-rich platelets, rather than to erbium-related defects. Electroluminescence is presented from a forward biased erbium-implanted Si0.87Ge0.13/Si structure at a drive current density of only 1.8 mA/cm2. 相似文献