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1.
The thermal expansions of polycrystalline samples of ferromagnetic YNi3 and paramagnetic YNi2 have been determined from 4.2 K up to 65 K employing the three-terminal-capacitance method. At low temperatures the expansion of YNi3 is dominated by a negative magnetic contribution which rapidly vanishes near the Curie temperature. The magnetovolume effects in YNi3 are discussed within the Stoner-Edwards-Wohlfarth model of very weak itinerant ferromagnetism.  相似文献   

2.
The values of Slater-Condon, spin-orbit, Racah, and Judd-Ofelt intensity parameters are reported. Observed energy levels and spectral intensities have been correlated with theoretically computed values. The nature of bonding in Nd3+ complexes is discussed. The oscillator strength of the hypersensitive transition decreases with a decrease of the Judd-Ofelt T2 parameter.  相似文献   

3.
The electronic absorption spectra of [(CH3)3NH] MnCl3.2H2O single crystals are reported in the 15,000–45,000 cm-1 region. In addition to the normally studied sextet → quartet transitions, special attention has been paid to the sextet → doublet transitions. Crystal field parameters evaluated (including the Trees' correction factor) to fit the observed spectra are B = 800, C = 2900, Dq = 680, and α = 76 cm-1.  相似文献   

4.
郑玉龙  甄聪棉  马丽  李秀玲  潘成福  侯登录 《物理学报》2011,60(11):117502-117502
在Si-Al2O3复合薄膜中观察到室温铁磁性.Si的体积百分比为15 %的Si-Al2O3复合薄膜的磁性最强.Si的含量影响样品的磁有序,在样品中观察到了明显的磁畴.在不同气氛下,对样品进行快速热退火.退火样品的磁性测试结果的差别表明氧空位不是样品铁磁性的主要来源.我们认为铁磁性来源于Si与Al2O3基质界面之间的缺陷的磁耦合.改变Si的含量可以改变缺陷密度,从而控制铁磁耦合强度. 关键词: 2O3薄膜')" href="#">Al2O3薄膜 室温铁磁性 掺杂 交换相互作用  相似文献   

5.
The microwave rotational spectra of the carbon-13 isotopic species of H2C3, H2C4, and H2C5 have been observed in a pulsed supersonic molecular beam by Fourier transform microwave spectroscopy. At high resolution all of the rotational lines exhibit hyperfine structure produced by the magnetic interaction between the nuclear spin of 13C and the overall rotation of the molecule. The component of the nuclear spin-rotation tensor along the a-inertial axis is large for most isotopic species, especially at the carbene carbon; at this position Caa is two to three times larger than at other substituted positions along the chain. In contrast to both H2C3 and H2C3, in H2C4Caa exhibits a pronounced alternation along the carbon chain backbone. Following detection of the five carbon-13 isotopic species and D2C5, an experimental structure (r0) has been determined to high accuracy for H2C5.  相似文献   

6.
In this work it is shown that ion irradiation of high-quality SrTiO3 single crystals can lead to room-temperature ferromagnetism. Structural analysis revealed a polycrystalline SrTiO3 layer, Sr2Ti6O13, or Ruddlesden-Popper like secondary phase at the sample surface induced by the irradiation. The lack of any measurable ferromagnetic secondary phases suggests defects are the origin of the observed ferromagnetic signal.  相似文献   

7.
The coadsorption of PH3 with H2, D2, O2 and H2O on Rh(100) has been studied using temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The adsorption and molecular desorption of PH3 is not affected by preadsorbed H2, D2 and O2. Preadsorbed PH3 blocks H2 desorption sites while postdosed PH3 displaces H2 (D21) from the Rh(100). When D2 and PH3 are coadsorbed, no D appears in desorbed phosphine. Preadsorbed O2 reduces the amount of H2 desorption (from PH3 decomposition) and increases the H2 desorption temperature. There is also some reaction between O(a) and H(a) to form water. Preexposure to H2O decreases the extent of PH3 adsorption and of PH3 decomposition.  相似文献   

8.
Magnetic characteristics of SmMn2Ge2 with a layer structure have been studied by magnetization measurements using single crystal. In the sequence of decreasing temperature, ferromagnetism is observed at 196 K ? T ? 348 K, collinear antiferromagnetism becomes stable for 64 K ? T < 196 K and reentrant ferromagnetism appears below 64 K. The appearance of such successive magnetic orderings are attributed to the variation of the shortest Mn-Mn distance due to thermal expansion and the existence of ferromagnetic coupling between the Sm moments in the intralayer which is dominant at low temperatures.  相似文献   

9.
The effect of hydrogen absorption on the magnetic properties of CeFe2 and ThFe3 was studied by magnetization measurements and by the 57Fe Mössbauer effect. In both cases an increase in the transition metal moment is observed. In CeFe2 the long range periodicity of the crystal lattice is lost whereas in ThFe3 a structural change occurs. Surprisingly, the magnetic anomaly observed in ThFe3 around 250 K is still present in the hydride.  相似文献   

10.
Differential susceptibility measurements were performed on a single crystal of RbCoCl3 · 2H2O. An anti-ferromagnetic ordering was found at 2.975 K.  相似文献   

11.
Infrared and Raman spectra of polycrystalline H3OUO2PO4·3 H2O (HUP) and its D and P18O4 derivatives, in the form of dense transparent disks and wet powder, have been investigated at various temperatures in the 100–300 K region. The bands due to framework vibrations are similar to those of KUP, whereas those for the protonic species are different. OH stretching and bending bands of the oxonium ion have been identified at 2920, 1740 and 1160 cm?1 in the low-temperature spectrum of HUP. Differential scanning calorimetry (DSC) and infrared (IR) intensity investigations show a phase transition between 274 and 260 K. The mechanism of the phase transition consists, as in the case of KUP, of ordering of the protonic species, which induces ordering of PO4 tetrahedra. The ordering can be influenced by excess water content, stacking faults and stress (ferroelastic behaviour is evidenced). The conductivity mechanism in HUP is discussed.  相似文献   

12.
The coefficient for pressure-induced vibrational absorption in H2ndash;H2 collisions was calculated for temperatures from 298 to 7000°K and wave numbers between 100 and 40,000 cm−1 for local thermodynamic equilibrium. Because only transitions with a net change of +1 vibrational quanta were considered, the absorption was centered near the fundamental at 4161 cm−1 in the infrared. The model included electronic configuration interaction, mechanical anharmonicity, vibration-rotation interaction, excited vibrational states, and more realistic intermolecular potential and line shapes than previously used. The integrated absorption coefficient at 3000°K was 2.1 times the previous theoretical value. An approximate formula for the absorption coefficient is given for rapid calculation.  相似文献   

13.
The simultaneous transitions of the v3 fundamental vibrations of CF4 and SF6 with the fundamental Q branch and S(1) line of H2 have been studied for various H2+CF4 and H2+SF6 mixtures at total pressures up to 185 bars. The integrated intensities are found to be proportional to the partial densities of the gas mixture components. The agreement between experimental and calculated intensities is generally better for the Kihara potential than for the Lennard-Jones potential.  相似文献   

14.
Recent theories by Luryi et al. and by Harris et al. for the energy levels of an isolated pair of ortho-H2 molecules in nearly pure solid para hydrogen are compared.  相似文献   

15.
Based on extensive Mossbauer effect (ME) and magnetization measurements, the orthorhombic AlFe2B2 was characterized as a ferromagnet (FM) because this character is evident as an onset of a FM transition at Tc=320 K and characteristic magnetizations isotherms below Tc. At liquid helium temperatures, the magnetization saturates to μsat≈1μB per Fe atom; a value which is half the one reported for the iron metal indicating a relatively more filled 3d band. The ME analysis revealed a hyperfine field H(0) of 88(2) kOe, an isomer shift (relative to Fe) of 0.50(2) mm/s, and a quadrupole parameter of 0.02 mm/s: all parameters extrapolated to zero Kelvin. The itinerant character of the magnetic moment will be discussed.  相似文献   

16.
The absolute photoabsorption cross sections of H2 and D2 have been measured photoelectrically in the wavelength region from 180 to 780 Å using synchrotron radiation. At photon wavelengths shorter than 650 Å, the absorption cross section was found to be structureless and to decrease montonically with decreasing wavelength. In this spectral region, both gases have nearly equal absorption cross sections, varying only within the experimental error. At photon wavelengths greater than λ 650 Å, structure is evident in the cross section of both gases and presumably corresponds to the Rydberg States reported by various authors.  相似文献   

17.
Antiferromagnetic resonance results on α-RbMnCl3 · 2H2O below the Néel temperature 4.56 K are reported. At T = 1.2K we find for the anisotropy fields Hc = 440 Oe and Ha = 1510 Oe. The spin flop field at T = 1.2K is 14.62 kOe.  相似文献   

18.
Results of magnetic measurements suggested that Bi2S3 and ZnS nanocrystalline powders prepared by hydrothermal method could possibly exhibit room temperature ferromagnetism. The measured saturation magnetization of the powders increases with an increase of annealing temperature from 300 to 500 °C. Ab initio calculations suggested that the cation vacancies on the surface of Bi2S3 and ZnS nanograins could be responsible for the observed magnetic moments. Heat-treatment of Bi2S3 or ZnS nanocrystalline powders in Bi or Zn vapor could bring about an enhancement of ferromagnetism. The calculation results indicated that the interstitial Bi or Zn atoms in Bi2S3 (0 0 1) or ZnS (0 0 1) surface could induce magnetic moments.  相似文献   

19.
Pure single crystals of MoO3 were carefully grown by physical vapor transport. The initial stages of the interaction of H2S with a MoO3 (010) surface were studied by RHEED and AES at low pressure p <133 Pa and at T < 700 K. Three main stages were found: (a) The formation of either a completely disordered sulphur adiayer (with pure H2S) or a superstructure MoO3(010)-[2 × 1]S (with H2S/H2). (b) A reduction of MoO3 producing oriented three-dimensional MoO2 islands, (c) An epitaxial overgrowth of MoS2 from the MoO2 three-dimensional crystallites.  相似文献   

20.
The electron paramagnetic resonance (EPR) of Nd2(SO4)3 · 8H2O and Sm2(SO4)3 · 8H2O doped with Gd3+ has been carried out at 273 K and the spin-Hamiltonian parameters are deduced. The zero field splittings have been computed and compared with those observed directly by Bogle and Symmons. It is found that the discrepancy in the zero field splittings. between computed and directly observed values falls within the range of linewidths of directly observed values.  相似文献   

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