The magnetic properties of polycrystalline samples of Mn1?tTtP (T = V, Cr, Fe and Co for 0.00 ≦ t ≦ 0.50) are studied by magnetic susceptibility, magnetization and neutron diffraction measurements. The magnetic phase diagrams of the Mn1?tTtP phases exhibit paramagnetic, ferromagnetic, helimagnetic and spin glass regions depending on temperature and substitution (T, t). The concentrated spin glass regions observed in Mn1?tVtP and Mn1?tCotP (0.30 ≦ t ≦ 0.50) are believed to result from the disorder in the metal sublattice. The variation of the magnetic moment of the ordered Mn1?tTtP phases with the substitution (T, t) is discussed. 相似文献
Thermoelectric power studies of the paramagnetic amorphous alloys NixZr1?x (x = 0.36, 0.40, 0.60, 0.65) are in agreement with predictions of the extended Ziman theory and indicate the multi-stage crystallization of some alloys. 相似文献
A ferromagnetic system with , where the interactions between nearest neighbours are isotropic (having Heisenberg character) and those between the next nearest neighbours anisotropic (Ising-like), is investigated. Using the effective hamiltonian approach we find the change in the critical temperature due to the inclusion of next nearest neighbour interactions of different character. The change is greatest in two dimensions where the critical temperature is shifted up from its zero value for a system with the Ising-like interactions switched off. We also calculate the Tc for a system with both nearest and next nearest neighbours interactions of the Ising-type. The results for the two models are compared. 相似文献
The crystal and magnetic properties of CoMnGe, CoFeGe, FeMnGe and NiFeGe compounds are investigated with X-ray, neutron diffraction, magnetometric and Mössbauer effect methods. All compounds have hexagonal Ni2In-type crystal structure and ferromagnetic properties at low temperatures (except for NiFeGe). Neutron diffraction experiments indicate that the compounds CoMnGe and CoFeGe have a collinear magnetic structure while FeMnGe a noncollinear. The magnetic moments are localized only on Mn and Fe atoms and lie in the basal plane. 相似文献
The main objective of this series of lectures is a discussion of the problem of quantization of systems with constraints, first studied by P.A.M. Dirac. I want to reinterprete Dirac's approach to quantization of constraints in the framework of geometric quantization, and then use it to discuss some aspects of quantized Yang-Mills fields. We begin with a review of geometric quantization and the implied relationship between the co-adjoint orbits and the irreducible unitary representations of Lie groups. Next, we discuss an intrinsic Hamiltonian formulation of a class of field theories which includes gauge theories and general relativity. Quantization of this class of field theories is discussed. Dirac's approach to quantization of constraints is reinterpreted in the framework of geometric quantization. 相似文献
In the present paper, we provide the conditions guaranteeing the generalization of so-called diauxic behaviour of solutions of ordinary differential equations (ODEs). This behaviour was described by Monod in 1949 in the context of bacterial growth. Then, a similar behaviour was observed and described referring to dynamic of CDK1 protein activity during cell cycle. The diauxic behaviour is described in terms of inflection points. 相似文献
The Turán number is the maximum number of edges in any -vertex graph that does not contain a subgraph isomorphic to . A wheel is a graph on vertices obtained from a by adding one vertex and making adjacent to all vertices of the . We obtain two exact values for small wheels: Given that is already known, this paper completes the spectrum for all wheels up to 7 vertices. In addition, we present the construction which gives us the lower bound in general case. 相似文献
We investigate the limiting behavior of sample central moments, examining the special cases where the limiting (as the sample size tends to infinity) distribution is degenerate. Parent (non-degenerate) distributions with this property are called singular, and we show in this article that the singular distributions contain at most three supporting points. Moreover, using the delta-method, we show that the (second-order) limiting distribution of sample central moments from a singular distribution is either a multiple, or a difference of two multiples of independent Chi-square random variables with one degree of freedom. Finally, we present a new characterization of normality through the asymptotic independence of the sample mean and all sample central moments.