The relation between microscopic properties (e.g., layer thickness, easy axis orientation) and the macroscopic magnetic properties such as remanent magnetization of the ferromagnetic multilayer system is investigated ...The relation between microscopic properties (e.g., layer thickness, easy axis orientation) and the macroscopic magnetic properties such as remanent magnetization of the ferromagnetic multilayer system is investigated based on a simple micromagnet approach. We concentrate on a multilayer design with periodic boundary condition, where alternating soft/hard layers build a nanostructured multilayer. For any easy axis direction in the soft and hard layers a simple explicit expression of remanence of the system has been derived analytically. We find that the remanence clearly depends on the thickness of the soft magnetic layer and is nearly independent of the thickness of hard magnetic layer. On the other hand, the remanence increases upon reducing the angle enclosed by the saturation magnetization and the easy axis directions of soft magnetic layer. However, it is unsensitive to the easy axis direction of hard magnetic layer, but there exists a maximum remanence for a certain easy axis direction of hard magnetic layer.展开更多
The weak-localization effect on the quasiparticle density of states (DOS) is studied with the diagrammatic technique in the binary-alloy model of disordered two-dimensional d-wave superconductors both in the Born and ...The weak-localization effect on the quasiparticle density of states (DOS) is studied with the diagrammatic technique in the binary-alloy model of disordered two-dimensional d-wave superconductors both in the Born and the unitary limits. We derive in details the expressions of the Goldstone modes (cooperon and diffuson) for quasiparticle diffuson. For generic Fermi surfaces, the DOS is shown to be subject to a quantum interference correction of logarithmic suppression. In the combined limit of unitarity and nested Fermi surface (the UN limit), it is found that the self-energy diagrams with two π-mode diffusons make additional contributions to the weak-localization effect, which has not been considered in the previous diagrammatic analysis. Due to the contributions of these new diagrams, the DOS in the UN limit is shown to have also a negative logarithmic correction, which is qualitatively different from the previous prediction.展开更多
We discuss the possibility of coexistence of d -wave superconductivity and ferromagnetism in a two-dimensional model on the assumption that the same electrons are responsible for both the pairing order and the ferroma...We discuss the possibility of coexistence of d -wave superconductivity and ferromagnetism in a two-dimensional model on the assumption that the same electrons are responsible for both the pairing order and the ferromagnetic order,The calculated results indicate that the coexistence is difficult to be realized in a uniform system.展开更多
We calculate the lowest-order quantum-interference correction to the density of states (DOS) of weakly-disordered two-dimensional (2D) tight-binding square lattices around half filling. The impurities are assumed to b...We calculate the lowest-order quantum-interference correction to the density of states (DOS) of weakly-disordered two-dimensional (2D) tight-binding square lattices around half filling. The impurities are assumed to be randomly distributed on small fractions of the sites, and have a-strong potential yielding a unitary-limit scattering. In addition to the usual diffusive modes in the retarded-advanced channel, there appear diffusive pi modes in the retarded-retarded (or advanced-advanced) channel due to the existence of particle-hole symmetry. It is found that the pi-mode diffuson gives rise to a logarithmic suppression to the DOS near the band center, which prevails over the positive correction contributed by pi-mode cooperon. As a result, the DOS is subject to a negative total correction. This result is qualitatively different from the divergent behavior of the DOS at the band center predicted previously for disordered 2D two-sublattice models with the particle-hole symmetry.展开更多
The possible geometrical structures and relative stabilities of semiconductor microclusters Ga\-\%n\%P\-\%n(n\%=1\_4) were studied by virtue of density functional calculations with generalized gradient approximation(B...The possible geometrical structures and relative stabilities of semiconductor microclusters Ga\-\%n\%P\-\%n(n\%=1\_4) were studied by virtue of density functional calculations with generalized gradient approximation(B3LYP). For the most stable isomers of Ga\-\%n\%P\-\%n(n\%=1\_4) clusters, the electronic structure, vibrational properties, dipole moment, polarizability and ionization potential were analyzed by means of HF, MP2, CISD and B3LYP methods with different basis sets.展开更多
In this paper, we analytically discuss the scaling properties of the average square end-to-end distance < R-2 > for anisotropic random walk in D-dimensional space (D >= 2), and the returning probability P-n(r...In this paper, we analytically discuss the scaling properties of the average square end-to-end distance < R-2 > for anisotropic random walk in D-dimensional space (D >= 2), and the returning probability P-n(r(0)) for the walker into a certain neighborhood of the origin. We will not only give the calculating formula for < R-2 > and P-n(r(0)), but also point out that if there is a symmetric axis for the distribution of the probability density of a single step displacement, we always obtain < R-perpendicular to n(2) > similar to n, where perpendicular to refers to the projections of the displacement perpendicular to each symmetric axes of the walk; in D-dimensional space with D symmetric axes perpendicular to each other, we always have < R-n(2)> similar to n and the random walk will be like a purely random motion; if the number of inter-perpendicular symmetric axis is smaller than < R-n(2)> similar to n(2) the dimensions of the space, we must have n for very large n and the walk will be like a ballistic motion. It is worth while to point out that unlike the isotropic random walk in one and two dimensions, which is certain to return into the neighborhood of the origin, generally there is only a nonzero probability for the anisotropic random walker in two dimensions to return to the neighborhood.展开更多
The inhomogeneity in a congrunet LiTaO3 crystal has been observed by transmission synchrotron topography.Many extraordinary regions exist in congruent LiTaO3 crystal and they often show diffraction intensity different...The inhomogeneity in a congrunet LiTaO3 crystal has been observed by transmission synchrotron topography.Many extraordinary regions exist in congruent LiTaO3 crystal and they often show diffraction intensity different from that of ordinary regions in synchrotron topographs.Differential thermal analysis indiates that the Curie temperature of the extraordinary region is lower than that of ordinary region,and the extraordinary region is really a high defect density region.The diffraction contrast of the extraordinary region in synchrotron topographs is explained qualitatively by a calculation at the selected wavelength.2001 Published by Elsevier Science B.V.展开更多
Large GdCa4O(BO3)3 crystal has been grown by the Czochralski method.The quality of GdCa4(BO3)3 crystal was assessed by white-beam synchrotron radiation topography.It has been found that there is a sub-grain boundary i...Large GdCa4O(BO3)3 crystal has been grown by the Czochralski method.The quality of GdCa4(BO3)3 crystal was assessed by white-beam synchrotron radiation topography.It has been found that there is a sub-grain boundary in the GdCa4O(BO3)3 crystal.The boundary divides the large GdCa4O(BO3)3 crystal into two individuals.Due to the misorientation between the two individuals,the image shifts can be observed in the synchrotron topopraphs.Based on the misorientation determined by high resolution X-ray diffractometer,the image shifts were calculated for several reflections.The calculations are in agreement with the measurements from the topogrphs very Well.In addition,the formation mechanism of sub-grain boundary is discussed.2001 Elsevier science B.V.All rights reserved.展开更多
The recent research work on domain structures and their dynamics in fenoelastic and ferroelectric crystals by white-beam synchrotron radiation topography is summarized.The real-time imaging,fine-beam Laue diffraction,...The recent research work on domain structures and their dynamics in fenoelastic and ferroelectric crystals by white-beam synchrotron radiation topography is summarized.The real-time imaging,fine-beam Laue diffraction,and anomalous-scattering topography were carried out to the study of the domain structures and phase transition in the ferroelastic NdP5O14 and LaP5O14,and ferroelectric KTa1-xNbxO3,(Ba0.25Sr0.75)0.9(K0.5Na0.5)0.2Nb2O6,and KTiOPO4 crystals.Some preliminary results are presented and discussed.展开更多
文摘The relation between microscopic properties (e.g., layer thickness, easy axis orientation) and the macroscopic magnetic properties such as remanent magnetization of the ferromagnetic multilayer system is investigated based on a simple micromagnet approach. We concentrate on a multilayer design with periodic boundary condition, where alternating soft/hard layers build a nanostructured multilayer. For any easy axis direction in the soft and hard layers a simple explicit expression of remanence of the system has been derived analytically. We find that the remanence clearly depends on the thickness of the soft magnetic layer and is nearly independent of the thickness of hard magnetic layer. On the other hand, the remanence increases upon reducing the angle enclosed by the saturation magnetization and the easy axis directions of soft magnetic layer. However, it is unsensitive to the easy axis direction of hard magnetic layer, but there exists a maximum remanence for a certain easy axis direction of hard magnetic layer.
文摘The weak-localization effect on the quasiparticle density of states (DOS) is studied with the diagrammatic technique in the binary-alloy model of disordered two-dimensional d-wave superconductors both in the Born and the unitary limits. We derive in details the expressions of the Goldstone modes (cooperon and diffuson) for quasiparticle diffuson. For generic Fermi surfaces, the DOS is shown to be subject to a quantum interference correction of logarithmic suppression. In the combined limit of unitarity and nested Fermi surface (the UN limit), it is found that the self-energy diagrams with two π-mode diffusons make additional contributions to the weak-localization effect, which has not been considered in the previous diagrammatic analysis. Due to the contributions of these new diagrams, the DOS in the UN limit is shown to have also a negative logarithmic correction, which is qualitatively different from the previous prediction.
文摘We discuss the possibility of coexistence of d -wave superconductivity and ferromagnetism in a two-dimensional model on the assumption that the same electrons are responsible for both the pairing order and the ferromagnetic order,The calculated results indicate that the coexistence is difficult to be realized in a uniform system.
文摘We calculate the lowest-order quantum-interference correction to the density of states (DOS) of weakly-disordered two-dimensional (2D) tight-binding square lattices around half filling. The impurities are assumed to be randomly distributed on small fractions of the sites, and have a-strong potential yielding a unitary-limit scattering. In addition to the usual diffusive modes in the retarded-advanced channel, there appear diffusive pi modes in the retarded-retarded (or advanced-advanced) channel due to the existence of particle-hole symmetry. It is found that the pi-mode diffuson gives rise to a logarithmic suppression to the DOS near the band center, which prevails over the positive correction contributed by pi-mode cooperon. As a result, the DOS is subject to a negative total correction. This result is qualitatively different from the divergent behavior of the DOS at the band center predicted previously for disordered 2D two-sublattice models with the particle-hole symmetry.
基金Supported by the West Visiting Scholar Foundation of the Educational Ministry of China and the Natiional NaturalScience Foundation of China(No.10 3470 0 7)
文摘The possible geometrical structures and relative stabilities of semiconductor microclusters Ga\-\%n\%P\-\%n(n\%=1\_4) were studied by virtue of density functional calculations with generalized gradient approximation(B3LYP). For the most stable isomers of Ga\-\%n\%P\-\%n(n\%=1\_4) clusters, the electronic structure, vibrational properties, dipole moment, polarizability and ionization potential were analyzed by means of HF, MP2, CISD and B3LYP methods with different basis sets.
文摘In this paper, we analytically discuss the scaling properties of the average square end-to-end distance < R-2 > for anisotropic random walk in D-dimensional space (D >= 2), and the returning probability P-n(r(0)) for the walker into a certain neighborhood of the origin. We will not only give the calculating formula for < R-2 > and P-n(r(0)), but also point out that if there is a symmetric axis for the distribution of the probability density of a single step displacement, we always obtain < R-perpendicular to n(2) > similar to n, where perpendicular to refers to the projections of the displacement perpendicular to each symmetric axes of the walk; in D-dimensional space with D symmetric axes perpendicular to each other, we always have < R-n(2)> similar to n and the random walk will be like a purely random motion; if the number of inter-perpendicular symmetric axis is smaller than < R-n(2)> similar to n(2) the dimensions of the space, we must have n for very large n and the walk will be like a ballistic motion. It is worth while to point out that unlike the isotropic random walk in one and two dimensions, which is certain to return into the neighborhood of the origin, generally there is only a nonzero probability for the anisotropic random walker in two dimensions to return to the neighborhood.
文摘The inhomogeneity in a congrunet LiTaO3 crystal has been observed by transmission synchrotron topography.Many extraordinary regions exist in congruent LiTaO3 crystal and they often show diffraction intensity different from that of ordinary regions in synchrotron topographs.Differential thermal analysis indiates that the Curie temperature of the extraordinary region is lower than that of ordinary region,and the extraordinary region is really a high defect density region.The diffraction contrast of the extraordinary region in synchrotron topographs is explained qualitatively by a calculation at the selected wavelength.2001 Published by Elsevier Science B.V.
文摘Large GdCa4O(BO3)3 crystal has been grown by the Czochralski method.The quality of GdCa4(BO3)3 crystal was assessed by white-beam synchrotron radiation topography.It has been found that there is a sub-grain boundary in the GdCa4O(BO3)3 crystal.The boundary divides the large GdCa4O(BO3)3 crystal into two individuals.Due to the misorientation between the two individuals,the image shifts can be observed in the synchrotron topopraphs.Based on the misorientation determined by high resolution X-ray diffractometer,the image shifts were calculated for several reflections.The calculations are in agreement with the measurements from the topogrphs very Well.In addition,the formation mechanism of sub-grain boundary is discussed.2001 Elsevier science B.V.All rights reserved.
文摘The recent research work on domain structures and their dynamics in fenoelastic and ferroelectric crystals by white-beam synchrotron radiation topography is summarized.The real-time imaging,fine-beam Laue diffraction,and anomalous-scattering topography were carried out to the study of the domain structures and phase transition in the ferroelastic NdP5O14 and LaP5O14,and ferroelectric KTa1-xNbxO3,(Ba0.25Sr0.75)0.9(K0.5Na0.5)0.2Nb2O6,and KTiOPO4 crystals.Some preliminary results are presented and discussed.
