Showing papers on "Spin-½ published in 1972"
TL;DR: In this article, a spin dependent one-electron potential pertinent to ground state properties is obtained from calculations of the total energy per electron made with a 'bubble' (or random phase) type of dielectric function.
Abstract: The local density theory is developed by Hohenberg, Kohn and Sham is extended to the spin polarized case. A spin dependent one- electron potential pertinent to ground state properties is obtained from calculations of the total energy per electron made with a 'bubble' (or random phase) type of dielectric function. The potential is found to be well represented by an analytic expression corresponding to a shifted and rescaled spin dependent Slater potential. To test this potential the momentum dependent spin susceptibility of an electron gas is calculated. The results compare favourably with available information from other calculations and from experiment. The potential obtained in this paper should be useful for split band calculations of magnetic materials.
3,750 citations
TL;DR: In this paper, it was shown that for an Ising spin system of arbitrary spin with a ferromagnetic pair interaction and a periodic external magnetic field there is a unique equilibrium state if and only if the magnetization is continuous with respect to a uniform change in the external field.
Abstract: We show that for an Ising spin system of arbitrary spin with a ferromagnetic pair interaction and a “periodic” external magnetic field there is a unique equilibrium state if and only if the magnetization is continuous with respect to a uniform change in the external field. Hence, if the critical temperatureTc is defined as the temperature where the spontaneous magnetization (which is a non-increasing function of the temperature) becomes positive, then the equilibrium state is unique forT>Tc and is non-unique forT Tc.
174 citations
TL;DR: In this paper, the coupled Bloch equations appropriate to conduction-electron spin resonance are derived rigorously to second order in $J$ with the result that correct static susceptibilities are obtained, and the instantaneous magnetizations are not proportional to the effective magnetic fields causing the magnetizations to precess.
Abstract: The scheme of Kadanoff and Baym is shown to be useful for the rigorous derivation of Bloch or Boltzmann equations for spin systems. The scheme is applied to a system of conduction electrons in a metal interacting via an exchange interaction $J$ with a low density of local spins. The coupled Bloch equations appropriate to conduction-electron spin resonance are derived rigorously to second order in $J$. The prominent features of the derived equations are that (i) the disturbed magnetizations are shown to relax to the instantaneous local equilibrium magnetization with the result that correct static susceptibilities are obtained, (ii) the instantaneous magnetizations are not proportional to the effective magnetic fields causing the magnetizations to precess, and (iii) the equations are consistent with conservation of the total magnetization.
148 citations
135 citations
TL;DR: In this article, critical indices for isotropic systems of $n$-dimensional spins in ($d=4\ensuremath{-}\ensureMath{\epsilon}$)-dimensional lattices are calculated to order the spin probability distribution.
Abstract: Critical indices for isotropic systems of $n$-dimensional spins in ($d=4\ensuremath{-}\ensuremath{\epsilon}$)-dimensional lattices are calculated to order $\ensuremath{\epsilon}$. All critical indices corresponding to perturbations of the spin probability distribution are given. Such perturbations might arise from the effects of external or crystal fields on the spin system.
105 citations
TL;DR: In this paper, a more complete justification of the side-jump model is given, which is used to derive the isothermal Nernst coefficient, where the side jump is assumed to have the same value for spin disorder as for impurity or phonon scattering.
Abstract: We recently showed that an electron wave packet undergoes an abrupt, sideways jump $\ensuremath{\Delta}y$ during scattering in the presence of spin-orbit interaction. This causes the Hall effect in ferromagnets around room temperature (${R}_{s}\ensuremath{\propto}{\ensuremath{\rho}}^{2}$). The value of the side jump per collision ($\ensuremath{\Delta}y\ensuremath{\approx}{10}^{\ensuremath{-}10}$ m) seems the same for impurity and phonon scattering. A more complete justification of the side-jump model is given here. This model is used to derive the isothermal Nernst coefficient ${Q}_{s}^{\mathrm{is}}$, giving ${Q}_{s}^{\mathrm{is}}\ensuremath{\propto}\ensuremath{\rho}T$, where $\ensuremath{\rho}$ is the resistivity. If spin-disorder scattering is also introduced, then the Hall conductivity ${\ensuremath{\gamma}}_{\mathrm{Hs}}$ is not affected, but the Nernst coefficient becomes ${Q}_{s}^{\mathrm{is}}=\ensuremath{-}T(\ensuremath{\alpha}+\ensuremath{\beta}\ensuremath{\rho})$. This formula agrees with the data of Kondorskii and Vasileva on Fe, Ni, Co, Gd, and Fe-Ni. The side jump is assumed to have the same value for spin disorder as for impurity or phonon scattering. The constant $\ensuremath{\alpha}$ is predicted to exist even in pure metals, in agreement with the above data but not with the Kondorskii theory.
101 citations
TL;DR: In this paper, the angular distribution of the vector analysing power and the absolute cross section were measured for (d, p) reactions on 40Ca, 46Ti, 48Ti, 50Ti, 52Cr and 54Fe at deuteron energies of 10 or 11 MeV.
92 citations
Book•
01 Jan 1972
71 citations
70 citations
68 citations
TL;DR: The simplest covariant generalization of the scalar wave equation leads to significant pion creation and annihilation processes near an isotropic Friedmann-type singularity (such processes are negligible for particles of nonzero spin) as mentioned in this paper.
Abstract: The simplest covariant generalization of the scalar wave equation leads to significant pion creation and annihilation processes near an isotropic Friedmann-type singularity (such processes are negligible for particles of nonzero spin). Estimates for a plausible initial state yield pion creation of the same order of magnitude as obtained by Zeldovich near an anisotropic Kasner-type singularity.
TL;DR: In this article, a critical study of the behavior of a massive spin two charged particle in an external electromagnetic field is made, and a unique Lagrangian which does not increase the number of degrees of freedom required for the description of a spin two particle is presented.
TL;DR: In this paper, high temperature series expansions of the susceptibility and second moment of the 1/2, 1, 2 and infinite spin Ising models on a triangular lattice are obtained and the spin dependence of the critical indices gamma and nu investigated.
Abstract: High temperature series expansions of the susceptibility and second moment of the 1/2, 1, 2 and infinite spin Ising models on a triangular lattice are obtained and the spin dependence of the critical indices gamma and nu investigated.
TL;DR: In this paper, the ground state spin arrangements in magnetic compounds of the NaCl type structure are studied by consideration of exchange interactions between nearest neighbors (J 1 ) and between next-nearest neighbours (J 2 ).
Abstract: The ground state spin arrangements in magnetic compounds of the NaCl type structure are studied by consideration of exchange interactions between nearest neighbors ( J 1 ) and between next-nearest neighbors ( J 2 ). Ferromagnetic arrangement as well as antiferromagnetic arrangements of the first kind, second kind, and improved first kind are obtained in different intervals of the parameter γ= J 2 / J 1 . Each of the three antiferromagnetic arrangements is degenerate due to the cubic symmetry of the crystal and the spin arrangement indefinite. Since the monoxides of the iron group elements are slightly distorted below the Neel point, the relevant small changes in J 1 and J 2 are taken into account to see if the degeneracy is removed. It turns out that the degeneracy is removed partially or completely. Helical spin arrangements appear in certain intervals of γ. Finally, anisotropy energy of the form D S z 2 is taken into account, but the degeneracy still remains unlifted in some cases.
TL;DR: In this article, a stochastic model for the exciton motion which comprises both the coherent and the incoherent motion is presented. But the model is restricted to the case of two molecules and does not take into account the influence of the exchange interaction integral.
Abstract: We use a stochastic model for the exciton motion which comprises both the coherent and the incoherent motion. The incoherent part is taken care of by a stochastic process which allows the local excitation energy and the transition matrix element to fluctuate by means of a Markovian process. The interaction between the spins and their surroundings is described by the usual spin-Hamiltonian which is, however, simplified to a spin 1/2 particle (instead of the triplet state). In the present paper we solve exactly the two limiting cases of completely coherent and incoherent motion (for two molecules). In the incoherent case the influence of the exchange interaction integral is taken into account by perturbation theory. We find expressions which are immediately comparable with ESR-experimental data. This comparison and additional information derived from optical absorption measurements allow us to determine all free parameters of our model uniquely. In particular, the fluctuations of the exchange interaction integral (with strength γ1) play an important role. From these parameters we may furthermore calculate the correlation time of the proton spin resonance in agreement with experimental data. The results show clearly that at room temperature in anthracene crystals the exciton undergoes a hopping process.
TL;DR: In this paper, the experimental level energies of the ground state band in 152Gd and 153Gd were compared with predictions from various phenomenological models. But the experimental results were only qualitatively for the energies obtained experimentally in this band.
TL;DR: The first transition series diborides are isomorphous compounds from ScB 2 to MnB 2 and they all show metallic behaviour and are paramagnetic up to VB 2 ; CrB 2, on the contrary, is antiferromagnetic with a small magnetic moment value in the ordered state which suggests the occurrence of itinerant spin magnetism as mentioned in this paper.
TL;DR: In this paper, it was shown that there are four possible spin orderings for the one-dimensional Ising magnet with nearest and next-nearest-neighbor interactions.
TL;DR: In this paper, the spin-polarized electron liquid is used in the density-functional method of Kohn and Sham to get spin-dependent, local one-body potentials and static dielectric properties.
TL;DR: In this article, the authors summarized recent results about the linear response properties and comments on the role of the non-locality of the self-energy in one-electron potentials.
Abstract: This paper summarizes recent results how to obtain approximate one-electron potentials describing exchange and correlation which depend on the local electron density. Following the lines given by Hohenberg, Kohn and Sham explicit results are given in two versions of the theory; one to describe ground state properties and one for excitation energies. The extension to spin polarized systems is discussed and some new results are presented. The paper also summarizes recent results about the linear response properties and comments on the role of the non-locality of the self-energy.
TL;DR: In this paper, a Bogoliubov automorphism on the algebra of the free in field is used for the case of an external time-dependent electromagnetic (scalar) field.
Abstract: The unitary (pseudo unitary) time-evolution operator for a particle with spin half (zero) in an external time-dependent electromagnetic (scalar) field is used to generate a Bogoliubov automorphism on the algebra of the free in field. For the case of an electric external field (scalar field) a finite expression for Ωout is given and theS-matrix constructed. The latter is unitary and implements the Bogoliubov automorphism. Theorems by Shale and Stinespring are rederived.
Journal Article•
TL;DR: In this paper, the three intense near-infrared bands of Fe2+ in silicate garnets at approximately 4500, 6000, and 7800 cm-l were assigned to transitions from the d,\" orbital ground state to the d., n, ils\"t &rtd d,o orbitals respectively.
Abstract: The three intense near-infrared bands of Fe2+ in silicate garnets at approximately 4500, 6000, and 7800 cm-l are assigned to transitions from the d,\" orbital ground state to the d.,,-n, ils\"t &rtd d,o orbitals respectively. The temperature dependence of the band intensities implies that the transitions are vibronically coupled by phonons with frequencies of 835 and 695 cm-l. The mean frequency is a measure of Dq for the S-fold siie and decreases with increasing mean X-O distance. The frequency difrerence between the il,. and. d1, orbitals is shown to be a measure of the distortion of the 8-fold site. Revised crystal field stabilization energies for Fe2+ in garnet are 10.26 to 10.72 kcal/mole.
TL;DR: The spin and isospin dependent parts of the single-particle potential in nuclear matter are calculated at the Fermi surface with the Brueckner-Gammel-Thaler and the Reid soft core potential as discussed by the authors.
TL;DR: In this paper, the temperature dependence of the magnon sideband with respect to the intensity, shift and broadening is studied theoretically in the entire temperature range by using the moment expansion method.
Abstract: Temperature dependence of magnon sideband with respect to the intensity, shift and broadening is studied theoretically in the entire temperature range by using the moment expansion method. The assumption of the Neel state for the ground state of the antiferromagnets is reasonable for intensity and shift but is incapable of explaining the magnitude of the width. Numerical calculations are carried out for 6 A 1 g → 4 A 1 g , 4 E g transition of RbMnF 3 by means of the random phase decoupling approximation for spin correlation functions and the results are presented. The results agree with those of the spin wave theory at low temperatures. At the high temperature limit, both the intensity and shift also agree with those given by the pair spectra theory. The effect of exciton transfer is also considered. The numerical result of the shift is compared with experiments.
TL;DR: In this article, the light-cone analysis of deepinelastic electron-proton scattering is extended to non-spin-averaged scattering and scaling is deduced for the spin-dependent structure functions M2νG1 and Mν2G2.
Abstract: The light-cone analysis of deep-inelastic electron-proton scattering is extended to non-spin-averaged scattering. Scaling is deduced for the spin-dependent structure functions M2νG1 and Mν2G2. The connection between moments of the scaling functions and matrix elements of operators in the operator-product expansion is described in detail and leads to two sum rules for the scaling functions when the quark light-cone algebra of Fritzsch and Gell-Mann is assumed. Predictions of other models of scaling are briefly compared.
TL;DR: In this article, the exact solution of a stochastic model for the cyclic Ising chain of N spins 1 2 with nearest-neighbour interactions in the absence of a magnetic field is presented.