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1.
Upconversion phosphors are known as a material system that can convert near-infrared light into visible/ultraviolet emissions by sequentially absorbing multiple photons. The studies on upconversion materials often use two rare earth (RE) ions as a sensitizer-activator pair. We investigated the influences on luminescence intensity depending on Cr-doping content (x) of hexagonal NaLu0.98–xCrxF4Er0.02 (x = 0–0.9) upconversion material by substituting Lu3+ ions with Cr3+in the absence of Gd3+. The change in upconversion luminescence intensity appears with saddle-like shape. We suggest that Cr3+ ions play the dual role as a constituent in host lattice and a sensitizer in the upconversion process. Optimal conditions for gaining the strongest upconversion emission correspond to x = 0.3–0.5, where there are effective energy transfers between Cr3+ and Er3+ ions and CrEr dimers. Apart from these values, the emission intensity decreases rapidly which can be ascribed to the absence of multiple-photon absorption for the case of low Cr3+ contents, and to the coupling between Cr3+ and/or Er3+ ions for the case of high Cr3+ contents. Magnetization and electron-spin-resonant measurements were performed to understand the correlation between the optical and magnetic properties. 相似文献
2.
H. Flandorfer A. Kostikas P. Rogl C. Godart M. Giovannini A. Saccone R. Ferro 《Journal of Alloys and Compounds》1996,240(1-2):116-123
The structural and magnetic properties of a series of novel compounds in the ternary Ce---Mg---Y system have been studied by X-ray diffraction. SQUID magnetometry and XAS spectroscopy. The crystal structures of the compounds Ce0.34Y0.67Mg2 and Ce0.49Y0.51Mg4.7 have been refined by the Rietveld technique. Magnetic data are consistent with a tripositive ground state 2F5/2 for the cerium atom. The XAS measurements confirm this result. Crystal field effects are apparent in the magnetic data at temperatures below about 50 K in the compounds with higher Ce concentration. 相似文献
3.
4.
《International Journal of Hydrogen Energy》2022,47(11):7491-7498
The anomalous Hall effect of thin PdCo films (Pd0.8Co0.2 alloy films; 5, 15, and 30 nm thick) subjected to various hydrogen concentrations in the gas phase was investigated. The Hall voltage of the 15 and 30 nm thick PdCo films against an external magnetic field exhibited hysteresis, indicating the anomalous Hall effect of PdCo. The hydrogen absorption in the 5 nm PdCo film decreased the Hall voltage in all considered magnetic fields. Moreover, the slope of the Hall voltage around a zero magnetic field decreased. When N2 was used as the carrier gas, the slope was proportional to the logarithm of the hydrogen concentration. For dry air, the slope differed from and was similar to that for N2 below and above hydrogen concentrations of 0.5% and 1.0%, respectively. The adsorbed oxygen on the PdCo surface disturbed the dissolved hydrogen in PdCo at low hydrogen concentrations in dry air. 相似文献
5.
Koshi Takenaka Masayoshi Ichigo Taisuke Hamada Atsushi Ozawa Takashi Shibayama Tetsuya Inagaki 《Science and Technology of Advanced Materials》2014,15(1)
Magnetostructural correlations in antiperovskite manganese nitrides were investigated systematically for stoichiometric and solid solution Mn3Cu1?xAxN (A = Co, Ni, Zn, Ga, Ge, Rh, Pd, Ag, In, Sn or Sb). This class of nitrides is attracting great attention because of their giant negative thermal expansion, which is achieved by doping Ge or Sn into the A site as a relaxant of the sharp volume contraction on heating (spontaneous volume magnetostriction ωs) because of the magnetovolume effects. The physical background of large ωs and mechanism of how the volume contraction becomes gradual with temperature are central concerns for the physics and applications of these nitrides. An entire dataset of thermal expansion, crystal structure and magnetization demonstrates that the cubic triangular antiferromagnetic state is crucial for large ωs. The intimate relationship between ωs and the magnetic structure is discussed in terms of geometrical frustration related to the Mn6N octahedron and magnetic stress concept. The results presented herein also show that ωs depends on the number of d electrons in the A atom, suggesting the important role of the d orbitals of the A atom. Not all the dopants in the A site, but the elements that disturb the cubic triangular antiferromagnetic state, are effective in broadening the volume change. This fact suggests that instability neighboring the phase boundary is related to the broadening. The relation between the gradual volume change and the local structure anomaly is suggested by recent microprobe studies. 相似文献
6.
7.
Rachid Essehli Brahim El BaliSaid Benmokhtar Khalid BouzianeBouchaib Manoun Mouner Ahmed AbdalslamHelmut Ehrenberg 《Journal of Alloys and Compounds》2011,509(4):1163-1171
Crystal structures from two new phosphates Na4NiFe(PO4)3 (I) and Na2Ni2Fe(PO4)3 (II) have been determined by single crystal X-ray diffraction analysis. Compound (I) crystallizes in a rhombohedral system (S. G: R-3c, Z = 6, a = 8.7350(9) Å, c = 21.643(4) Å, R1 = 0.041, wR2=0.120). Compound (II) crystallizes in a monoclinic system (S. G: C2/c, Z = 4, a = 11.729(7) Å, b = 12.433(5) Å, c = 6.431(2) Å, β = 113.66(4)°, R1 = 0.043, wR2=0.111). The three-dimensional structure of (I) is closely related to the Nasicon structural type, consisting of corner sharing [(Ni/Fe)O6] octahedra and [PO4] tetrahedra forming [NiFe(PO4)3]4+ units which align in chains along the c-axis. The Na+ cations fill up trigonal antiprismatic sites within these chains. The crystal structure of (II) belongs to the alluaudite type. Its open framework results from [Ni2O10] units of edge-sharing [NiO6] octahedra, which alternate with [FeO6] octahedra that form infinite chains. Coordination of these chains yields two distinct tunnels in which site Na+.The magnetization data of compound (I) reveal antiferromagnetic (AFM) interactions by the onset of deviations from a Curie-Weiss behaviour at low temperature as confirmed by Mössbauer measurements performed at 4.2 K. The corresponding temperature dependence of the reciprocal susceptibility χ−1 follows a typical Curie-Weiss behaviour for T > 105 K. A canted AFM state is proposed for compound (II) below 46 K with a field-induced magnetic transition at H ≈ 19 kOe, revealed in the hysteresis loop measured at 5 K. This transition is most probably associated with a spin-flop transition. 相似文献
8.
Mark Huijben Alexander Brinkman Gertjan Koster Guus Rijnders Hans Hilgenkamp Dave H. A. Blank 《Advanced materials (Deerfield Beach, Fla.)》2009,21(17):1665-1677
A large variety of transport properties have been observed at the interface between the insulating oxides SrTiO3 and LaAlO3 such as insulation, 2D interface metallicity, 3D bulk metallicity, magnetic scattering, and superconductivity. The relation between the structure and the properties of the SrTiO3/LaAlO3 interface can be explained in a meaningful way by taking into account the relative contribution of three structural aspects: oxygen vacancies, structural deformations (including cation disorder), and electronic interface reconstruction. The emerging phase diagram is much richer than for related bulk oxides due to the occurrence of interface electronic reconstruction. The observation of this interface phenomenon is a display of recent advances in thin film deposition and characterization techniques, and provides an extension to the range of exceptional electronic properties of complex oxides. 相似文献
9.
M. P. Annaorazov S. A. Nikitin A. L. Tyurin S. A. Akopyan R. W. Myndyev 《International Journal of Refrigeration》2002,25(8):1034-1042
The heat-pumping scheme based on the 1st order antiferromagnetism–ferromagnetism transition induced in FeRh alloy by one-dimensional tensile stress is proposed. Using the model S–T diagram for this alloy, the heat-pump cycles are drawn up based both on the transition latent heat absorption and emission when the transition is induced isothermally and on the change in alloy's temperature when the transition is induced adiabatically by applying tensile stress. The calculated values of heat coefficient φ for the cycles are 30 at ΔT=5 К and 20 at ΔT=10 К, where ΔT is the difference between the temperature surrounding and that of the heat receiver. These values are achieved using the tensile stress of 1·109 Pa. The high values of φ make it possible to consider Fe–Rh alloys near the equiatomic composition as an effective refrigerant for elastocaloric heat-pumping near the room temperature. 相似文献
10.
Angela M. Gutierrez Rohit Bhandari Jiaying Weng Arnold Stromberg Thomas D. Dziubla J. Zach Hilt 《应用聚合物科学杂志》2020,137(37):49109
In this work, the development of novel magnetic nanocomposite microparticles (MNMs) via free radical polymerization for their application in the remediation of contaminated water is presented. Acrylated plant-based polyphenols, curcumin multiacrylate (CMA) and quercetin multiacrylate (QMA), were incorporated as functional monomers to create high affinity binding sites for the capture of polychlorinated biphenyls (PCBs), as a model pollutant. The MNMs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, dynamic light scattering, and UV–visible spectroscopy. The affinity of these novel materials for PCB 126 was evaluated and fitted to the nonlinear Langmuir model to determine binding affinities (KD). The results suggest the presence of the polyphenolic moieties enhances the binding affinity for PCB 126, with KD values comparable to that of antibodies. This demonstrates that these nanocomposite materials have promising potential as environmental remediation adsorbents for harmful contaminants. 相似文献