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111.
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本文采用水热法,分别以ZnO、Zn(OH)2为前驱物,添加一定量的MnCl4.4H2O和CuSO4.2H2O, 3mol/LKOH作矿化剂,温度430℃,填充度35%,反应24h,制备了Mn、Cu共掺ZnO晶体。当前驱物为Zn(OH)2时,所得晶体大部分为短柱状晶体,显露正负极面{0001}、{0001-}、负锥面-p{101-1-}和柱面m{1-010},长度约为30 ~50μm。少部分晶体为单锥六棱柱状,显露正锥面p{101-1},柱面m{1-010},负极面-c{0001-},晶体的长度约为100μm,长径比为5:1。当ZnO用作前驱物时,短柱状晶体长度大约为10 ~30μm,晶体的六棱对称性都出现较大的偏差。X射线荧光能谱分析表明,前驱物为ZnO、Zn(OH)2时,Mn离子含量在分别为3.19%和1.62%原子分数,没有检测到Cu离子。虽然Mn、Cu离子的掺入会明显影响晶体形态,磁性测量显示掺杂Mn、Cu的ZnO仍为反铁磁。 相似文献
114.
Dr. Maria R. Catalano Giuseppe Cucinotta Emanuela Schilirò Dr. Matteo Mannini Prof. Dr. Andrea Caneschi Dr. Raffaella Lo Nigro Emanuele Smecca Prof. Dr. Guglielmo G. Condorelli Prof. Dr. Graziella Malandrino 《ChemistryOpen》2015,4(4):523-532
Calcium-doped praseodymium manganite films (Pr0.7Ca0.3MnO3, PCMO) were prepared by metal-organic chemical vapor deposition (MOCVD) on SrTiO3 (001) and SrTiO3 (110) single-crystal substrates. Structural characterization through X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) analyses confirmed the formation of epitaxial PCMO phase films. Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) characterization was used to confirm lateral and vertical composition and the purity of the deposited films. Magnetic measurements, obtained in zero-field-cooling (ZFC) and field-cooling (FC) modes, provided evidence of the presence of a ferromagnetic (FM) transition temperature, which was correlated to the transport properties of the film. The functional properties of the deposited films, combined with the structural and chemical characterization collected data, indicate that the MOCVD approach represents a suitable route for the growth of pure, good quality PCMO for the fabrication of novel spintronic devices. 相似文献
115.
Inside Cover: New Classes of Ferromagnetic Materials with Exclusively End‐on Azido Bridges: From Single‐Molecule Magnets to 2 D Molecule‐Based Magnets (Chem. Eur. J. 43/2014)
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117.
Subir Sachdev 《Pramana》2002,58(2):285-292
We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron
gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides
in the plane orthogonal to the ferromagnetic moment. We argue that a quantum transition involving the destruction of the spinglass
order in an applied in-plane magnetic field offers a natural explanation of some features of recent magnetoconductance measurements.
We present a quantum field theory for such a transition and compute its mean field properties. 相似文献
118.
Spin-polarized photoemission with circularly polarized light represents a relatively new technique in surface science. It became feasible with the increased availability of circularly polarized light in the vacuum ultraviolet and soft X-ray regime, generated in dedicated synchrotron radiation facilities. Another important ingredient was the development of efficient electron spin polarization detectors. Supported by group theoretical considerations, this technique was first employed to study the process of optical spin orientation in single crystalline non-magnetic materials. In these samples, spin-dependent effects arise solely from spin-orbit coupling. The experiments revealed the strong influence of spin-orbit coupling on the details of the electronic band structure, such as the symmetry character of the electronic wave functions, hybridization phenomena, and the behavior of degeneracies. The results opened the way to a detailed understanding of the electronic structure and permit a rigorous test of both state-of-the-art bulk band theories and fully relativistic photoemission calculations. Since 1990, spin-polarized photoemission with circularly polarized light is also used to investigate ferromagnetic systems. These experiments led to the discovery of the counterpart of optical spin orientation in ferromagnets, namely, the magnetic dichroisms. Magnetic dichroism means that the spin-dependent photoexcitation from a ferromagnetically ordered system manifests itself already in the photoelectron intensity distributions. Because of this particular property, techniques based on magnetic dichroisms are currently receiving wide interest in the spectroscopic investigation of magnetic systems and phenomena.
The following article reviews the current status of the field of spin- and angle-resolved photoemission from solids using circularly polarized radiation. We survey the development of this technique over the last 10 years, covering its applications to both non-magnetic and ferromagnetic systems. 相似文献
119.
Hal Tasaki 《Journal of statistical physics》1996,84(3-4):535-653
Whether spin-independent Coulomb interaction in an electron system can be the origin of ferromagnetism has been an open problem for a long time. Recently, a constructive approach to this problem has been developed, and the existence of ferromagnetism in the ground states of certain Hubbard models was established rigorously. A special feature of these Hubbard models is that their lowest bands (in the corresponding single-electron problems) are completely flat. Here we study models obtained by adding small but arbitrary translation-invariant perturbation to the hopping Hamiltonian of these flat-band models. The resulting models have nearly flat lowest bands. We prove that the ferromagnetic state is stable against a single-spin flip provided that Coulomb interactionU is sufficiently large. (It is easily found that the same state is unstable against a single-spin flip ifU is small enough.) We also prove upper and lower bounds for the dispersion relation of the lowest energy eigenstate with a single flipped spin, which bounds establish that the model has healthy spin-wave excitation. It is notable that the (local) stability of ferromagnetism is proved in nonsingular Hubbard models, in which we must overcome competition between the kinetic energy and the Coulomb interaction. We also note that this is one of the very few rigorous and robust results which deal with truly non-perturbative phenomena in many-electron systems. The local stability strongly suggests that the Hubbard models with nearly flat bands have ferromagnetic ground states. We believe that the present models can be studied as paradigm models for (insulating) ferromagnetism in itinerant electron systems. 相似文献
120.
The generalized analysis of a change in magnetic properties of organometallosiloxanes as a function of the number of metal
atoms in their molecules (on going from mono- and binuclear to polynuclear crystalline and polymeric compounds) is presented.
The relation between the magnetic characteristics and structural parameters of metal-containing fragments is studied. The
factors affecting the formation of exchange-coupled ionic pairs and clusters in polymeric systems are analyzed. The ways to
the organization of magnetic phases in polymeric systems are considered: the choice of conditions of chemical synthesis, the
organization of metal atoms in a common spin system upon incorporation of conducting coordinating additives, and thermocondensation
and reduction processes leading to the formation of a metallic phase dispersed in a silicon dioxide matrix.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1432–1442, August, 1997. 相似文献