Magnetic moments of <Superscript>33</Superscript>Mg in the time-odd relativistic mean field approach

The configuration-fixed deformation constrained relativistic mean field approach with time-odd component has been applied to investigate the ground state properties of 33Mg with effective interaction PK1.The ground state of 33Mg has been found to be prolate deformed,β2=0.23,with the odd neutron in 1/2[330] orbital and the energy -251.85 MeV which is close to the data -252.06 MeV.The magnetic moment -0.9134 μN is obtained with the effective electromagnetic current which well reproduces the data -0.7456 μN se...     

Neutron single-particle characteristics of Ag isotopes in the dispersive optical model

The neutron dispersive optical potential for Ag isotopes is constructed for a wide range of variation in the N number. Good agreement with the experimental data on the scattering of neutrons by ¹⁰⁷Аg isotopes, and on single-particle energies and the probabilities of subshell occupation near the Fermi energy, is obtained for stable isotopes ^{107, 109}Ag using the dispersive optical model. Calculations that predict the evolution of the neutron single-particle energies up to the boundary of neutron stability are performed. It is shown that new magic number N = 56 (for Z = 40) disappears upon moving from Zr to Sn in an isotonic chain with N = 56, due to rapid deepening of level 1g _7/2.     

Spin excitations in the EuxSr1−xS spin glass system: Influence of the dipolar interactions

The spin excitations of an Eu_0.4Sr_0.6S spin glass are calculated numerically, taking also the dipole interaction into account, in addition to nearest- and next-nearest neighbour exchange. The influence of this additional interaction is found to be small and thus apparently cannot explain the present discrepancies between the theory and inelastic neutron scattering experiments. Switching on the dipole interaction corresponds to an effective enhancement of the Eu concentration of roughly 0.08.     

Evidence of ferromagnetic domains in the perovskite La0.7Sr0.3Co0.9Mn0.1O3

The magnetic and electronic ground states of the polycrystalline perovskite compound La_0.7Sr_0.3Co_0.9Mn_0.1O₃ have been studied using AC susceptibility, resistivity and neutron depolarization techniques. Results of neutron depolarization study establish the existence of ferromagnetic domains of ∼3 μm size below 180 K. The substitution of 10 at% Mn ions at the Co site in the compound La_0.7Sr_0.3CoO₃ reduces the effective e_g electron transfer and suppresses the double exchange interaction. The competition between the reduced ferromagnetic double exchange interaction and the coexisting antiferromagnetic interaction along with the random nature of substitution leads to a randomly canted ferromagnetic ground state for the substituted compound. Resistivity study confirms that the randomly canted ferromagnetic ground state is insulating.     

Study of magnetic properties of Pd<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>0.95</Subscript>Mn<Subscript>0.05</Subscript> alloy using polarized muons and neutrons

The Pd_1?x Fe _x )_0.95Mn_0.05 alloy with random competing interaction was studied by measuring the muon spin relaxation in an external transverse magnetic field and in a zero magnetic field. Using the measured temperature dependence of the dynamic relaxation rate λ and the characteristics of the distribution of local static fields, the phase states of the sample under study are refined. In particular, it is shown that the ferromagnetic and spin-glass states coexist simultaneously in the sample below 25 K. Combined studies of the sample using the μSR and neutron depolarization methods made it possible to determine the size of magnetic inhomogeneities to be 2–6 μm in the temperature range 5–40 K.     

Approximation of the microscopic effective pairing interaction by the off-shell T matrix for free nucleon-nucleon scattering

The effective pairing interaction in the ¹ S ₀ channel as calculated microscopically within the Brueckner method for a planar slab of nuclear matter by using the separable version of the Paris nucleon-nucleon potential is investigated. The effective interaction is determined for the model space including all negative-energy single-particle states. An analysis is performed for two values of the chemical potential, μ=?8 and ?4 MeV. It is shown that, to a high precision, the effective interaction can be approximated by the off-shell T matrix for free nucleon-nucleon interaction, the T matrix in question being taken at a negative value of the total energy of two nucleons E=2μ.     

Neutron Matter Properties Using Skyrme Interaction

The purpose of the present work is to extend earlier nuclear matter calculations to study the properties of neutron matter. The binding energy per particle, symmetry energy, single particle potential, effective mass, and magnetic susceptibility are calculated using a modified Skyrme interaction. These are calculated as a function of the Fermi momentum k_f in the range 0 < k_f < 2 fm^?1. Two sets of the interaction parameters are obtained by fitting the interaction parameters using the available information on neutron matter. Relativistic corrections to the order 1/c² are also calculated. The relativistic corrections are very small and they increase as k_f is increased.     

3PF2 neutron superfluidity in neutron stars and three-body force effect

We investigate the ^3PF2 neutron superfluidity in H-stable neutron star matter and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V18 potential supplemented with a microscopic three-body force as the realistic nucleon-nucleon interaction. We have concentrated on studying the threebody force effect on the ^3PF2 neutron pairing gap. It is found that the three-body force effect is to enhance remarkably the ^3PF2 neutron superfluidity in neutron star matter and neutron stars.     

Self-consistent description of the inner crust of a neutron star with allowance for superfluidity effects

Within the Wigner-Seitz approximation, a self-consistent fully quantum-mechanical calculation of the structure of the inner crust of a neutron star is performed over a wide range of densities with allowance for superfluidity effects. Within the approach used, the Wigner-Seitz cell consists of a nuclear-like cluster surrounded by a nearly uniform neutron gas. An effective energy functional is constructed by matching, at the cluster surface, the realistic phenomenological nuclear functional for the cluster due to S. A. Fayans and his coauthors and the energy functional calculated microscopically for neutron matter. The microscopic component of the functional is calculated within the Brueckner method by using the v18 Argonne interaction.     

Role of magnetism in the formation of a short-range order in an Fe-Ga alloy

The formation of a short-range order in an Fe-Ga bcc alloy has been studied by Monte Carlo simulation with the use of effective interaction potentials calculated within the density functional theory for the ferromagnetic and paramagnetic states. It has been found that the pronounced short-range order of the D0₃ type is formed at Ga concentrations close to the boundary of the two-phase region at T < T _c, whereas no short-range order is observed at T < T _c. The results obtained are in agreement with the experimental X-ray diffraction analysis. The relation of the features of the short-range order in the Fe-Ga alloy to the magnetostriction value has been discussed.     

Pionic x-rays and the neutron radius of 44Ca

Differences between strong interaction level shifts and widths for 2p states in pionic atoms of ^44,40Ca have been measured. Analysis in terms of an effective pion-nucleus potential leads to a difference in neutron rms radii of r_n(44)?r_n(40) = 0.05 ± 0.05 fm.     

Mössbauer effect and nuclear moments of the 75 keV state of Dy161 and the 81 keV state of Dy162

The Mössbauer effect of theγ rays from the 74.5 keV state of Dy¹⁶¹ and the 80.7 keV state of Dy¹⁶² has been investigated. From hyperfine splitting patterns the magnetic moments μ(75 keV)=?(0.39±0.04) nm, μ(81 keV)=+(0.74±0.08) nm and the quadrupole momentQ(75 keV)=+(1.4±0.2)b have been determined. For the odd neutron nucleus Dy¹⁶¹ an effective spin g factorg _{s, eff}=0.76 g_{s, free} is deduced for the 75 keV level.     

Mössbauer-effect investigation of the magnetic phases in the Mn1−xCrxSb system

The magnetic phases of the Mn_1?xCr_xSb system, at 4.2°K, have been investigated through the Mössbauer effect in Sb¹²¹. The ferromagnetic component of the magnetization induces an effective magnetic field at the Sb nuclei which is observed to decrease with increase in Cr concentration. Bulk magnetization and neutron diffraction data are given for comparison and the ‘double exchange’ interaction model is considered in the discussion of the results.     

Nuclear symmetry energy in terms of single-nucleon potential and its effect on the proton fraction of <Emphasis Type="Italic">β</Emphasis>-stable <Emphasis Type="Italic">npeμ</Emphasis> matter

Momentum and density dependence of single-nucleon potential u_τ (k, ρ, β) is analyzed using a density dependent finite range effective interaction of the Yukawa form. Depending on the choice of the strength parameters of exchange interaction, two different trends of the momentum dependence of nuclear symmetry potential are noticed which lead to two opposite types of neutron and proton effective mass splitting. The 2nd-order and 4th-order symmetry energy of isospin asymmetric nuclear matter are expressed analytically in terms of the single-nucleon potential. Two distinct behavior of the density dependence of 2nd-order and 4th-order symmetry energy are observed depending on neutron and proton effective mass splitting. It is also found that the 4th-order symmetry energy has a significant contribution towards the proton fraction of β-stable npeμ matter at high densities.     

π凝聚态中的弱过程对中子星振动的阻尼效应

本文主要讨论了中子星内部发生从正常中子物态到π凝聚物态相变所产生的星体振动的阻尼,由弱作用反应u(p₁)→u(p₂)+e^-+v_e和u(p₁)+e^-→u(p₂)+v_e算出振动阻尼时标,并考虑了中子星内部的热演化。 关键词：     

Polarised neutron diffraction study of Mn1.09Sb

In order to study the influence of interstitial site occupancy on the electronic structure of MnSb, a polarised neutron diffraction experiment was performed on Mn_1.09Sb. The composition of the sample was obtained from the refinement of single crystal neutron diffraction data. The polarised neutron diffraction experiment yielded unpaired electron populations of the levels a^t_1g, e_g^t and e_g as follows: μ_x0 = 0.57 μ_B, μ_x± = 1.60 μ_B, μ_u± = 1.28μ_B. The comparison of these numbers with results of Yamaguchi et al shows that the spin density for this composition is reduced for the low energy level a^t_1g. This finding is interpreted by an occupation of minority spin states by electrons of the interstitial Mn atoms. In agreement with this, increasing Mn excess leads to a decreasing magnetic moment magnitude/Mn-atom and to a contraction of the lattice parameter c, indicating the strengthening of the Mn-Mn bond in [001].     

填充式方钴矿化合物CeOs4Sb12近藤相互作用的非弹性中子散射研究

CeOs₄Sb₁₂晶体中由于导电电子与Ce³⁺ 4f¹电子之间存在c-f杂化作用导致费米面附近存在能量间隙.这种c-f近藤相互作用和能量间隙是理解CeOs₄Sb₁₂物理性质，如近藤绝缘体行为、Ce³⁺磁矩在低温下猝灭以及重费米性等电、磁性质的关键.当用LAM-D中子谱仪对粉末CeOs₄Sb₁₂进行测量时，可以得到不同温度下CeOs₄Sb₁₂的非弹性中子散射谱.结果表明CeOs₄Sb₁₂中存在近藤相互作用，其作用强度为3.1 meV，证实了CeOs₄Sb₁₂为近藤绝缘体.中子测量得出CeOs₄Sb₁₂德拜温度为317 K. 关键词： 非弹性中子散射 填充式方钴矿 近藤绝缘体     

A realistic model of superfluidity in the neutron star inner crust

A semi-microscopic self-consistent quantum approach developed recently to describe the inner-crust structure of neutron stars within the Wigner-Seitz (WS) method with the explicit inclusion of neutron and proton pairing correlations is further developed. In this approach, the generalized energy functional is used which contains the anomalous term describing the pairing. It is constructed by matching the realistic phenomenological functional by Fayans et al. for describing the nuclear-type cluster in the center of the WS cell with the one calculated microscopically for neutron matter. Previously, the anomalous part of the latter was calculated within the BCS approximation. In this work corrections to the BCS theory which are known from the many-body theory of pairing in neutron matter are included into the energy functional in an approximate way. These modifications have a sizable influence on the equilibrium configuration of the inner crust, i.e. on the proton charge Z and the radius R _c of the WS cell. The effects are quite significant in the region where the neutron pairing gap is larger.     

Equation of state for pion-condensed neutron matter at finite temperature

The equation of state for neutron matter in the presence of a pion condensate is investigated at finite, but small temperature within the σ model. It is found that a transition of van der Waals type takes place at low temperature for sufficiently strong effective p-wave interaction, which disappears however beyond a critical temperature T_c. Within a wide variety of model assumptions, an upper limit of about 50 MeV is found for T_c.