Showing papers on "Spin wave published in 1988"
TL;DR: The supersymmetrical gauge theory of strongly correlated electronic systems, based on a geometrical approach to the quantization of the Hubbard model, is presented and it is shown that topological magnetic excitations induce the long-distance interaction between the charged particles.
Abstract: The supersymmetrical gauge theory of strongly correlated electronic systems, based on a geometrical approach to the quantization of the Hubbard model, is presented. It is shown that topological magnetic excitations induce the long-distance interaction between the charged particles. This interaction, depending on the statistics of the magnetic excitations, leads to the confinement or statistical transmutation phenomenon and finally to the superconductivity. The long-wave theory of the short-range-order antiferromagnetic insulator state is proposed.
308 citations
TL;DR: In this paper, a method has been developed for calculating energies by full spin projection of unrestricted Mdler-Plesset perturbation theory wave functions, which has been tested on bond dissociation potentials of LiH and HF and on symmetrically stretched H20.
Abstract: A method has been developed for calculating energies by full spin projection of unrestricted Mdler-Plesset perturbation theory wave functions. The spin projection technique has been tested on bond dissociation potentials of LiH and HF and on symmetrically stretched H20. In the region where the UHF wave function is more stable than the RHF wave function, spin projected UMPn energies of low order (n I 4) have smaller errors than the corresponding spin restricted MPn and unprojected UMPn energies, when compared to full configuration interaction calculations. For higher order perturbation theory, spin restricted MPn energies may be more accurate than spin projected UMPn, but only for limited region near the RHF/UHF instability. An approximate spin projected UMPn formalism developed earlier yields energies that are in good agreement with the-present full spin projected UMPn calculations. A formula for spin projected energies in the coupled clusters approach is also presented. It is shown that annihilation of any single spin contaminant leaves the CCSD energy una1 tered.
255 citations
TL;DR: In this paper, the authors reported the observation of spin-pair excitations in Ba/sub 2/YCu/sub 3/O/sub 6+//sub delta with delta in the range 0.0--0.9.
Abstract: We report observation of spin-pair excitations in Ba/sub 2/YCu/sub 3/O/sub 6+//sub delta/, with delta in the range 0.0--0.9. The frequency of the excitations, and hence the value of the exchange constant, J = 950 cm/sup -1/, is similar to that reported recently for (nonsuperconducting) La/sub 2/CuO/sub 4/. The present observation of magnetic excitations in a superconducting material, and of their evolution as a function of delta, demonstrate a large influence of carrier concentration on the spin-fluctuation dynamics.
243 citations
TL;DR: The ground state of a quantum vacancy in a 2D antiferromagnet is found to involve a long-range dipolar distortion of the staggered magnetization, and an effective Hamiltonian for vacancies interacting with long-wavelength spin waves is derived.
Abstract: The ground state of a quantum vacancy in a 2D antiferromagnet is found to involve a long-range dipolar distortion of the staggered magnetization. An effective Hamiltonian of vacancies interacting with long-wavelength spin waves is derived. The implications for the anitferromagnetic long-range order are discussed.
240 citations
222 citations
Book•
01 Apr 1988
TL;DR: The theory of magnetic excitations in disordered systems (IYa Korenblit and EF Shender) was introduced by as discussed by the authors, where the spin dynamics of amorphous magnets were investigated.
Abstract: Part II - Preface Contents Introduction 1 Spin-wave resonance in metals (Z Frait and D Fraitova) 2 Excitations in low-dimensional magnetic systems (VL Pokrovsky, MV Feigel'man and AM Tsvelick) 3 Theory of magnetic excitations in disordered systems (IYa Korenblit and EF Shender) 4 Spin dynamics of amorphous magnets (JW Lynn and JJ Rhyne) 5 Magnetic excitations in spin glasses (SM Shapiro) 6 Magnetic impuritons in antiferromagnetic dielectric crystals (VV Eremenko and VM Naumenko) 7 Magnetoelastic excitations (VG Bar'yakhtar and EA Turov) 8 Nuclear spin excitations (MI Kurkin and EA Turov) Author index Subject index Materials index Cumulative index
95 citations
TL;DR: In this article, the authors derived a microscopic model representing a coupled system of spin degrees of freedom on O sites and a low concentration of mobile holes, assuming that the predominant charge carriers in superconducting cooper oxides are holes on the O sites.
94 citations
88 citations
TL;DR: In this article, a theory of periodic multilayers consisting of two alternating ferromagnetic materials with different transition temperatures is presented, based on an inhomogeneous Ginzburg-Landau functional, where the GL coefficients are chosen to model the alternating layers and interface interactions.
Abstract: A theory of periodic multilayers consisting of two alternating ferromagnetic materials with different transition temperatures is presented. The theory is based on an inhomogeneous Ginzburg-Landau (GL) functional, where the GL coefficients are chosen to model the alternating layers and interface interactions. The transition temperature of the composite material is derived by use of the linear stability analysis of the inhomogeneous GL functional. The static magnetization profiles for different temperatures are calculated analytically. It is shown that the magnetization penetrating into the low-temperature ferromagnet falls off inversely with distance close to ${T}_{1}$ and exponentially far above ${T}_{1}$, where ${T}_{1}$ is the lower transition temperature. We also consider the average magnetization of this multilayer system and its characteristic temperature dependence. The spin dynamics are studied by use of a generalized Bloch equation. Different limiting cases as well as the general situation with both dipolar and exchange interactions are considered. The magnon dispersion relation is computed and by symmetry considerations, it is shown that the gaps vanish at certain values of the wave vector k. The inelastic neutron scattering cross section is calculated. With appropriate modifications the theory can be applied to other systems undergoing phase transitions, such as ferroelectrics.
84 citations
TL;DR: In this article, general dispersion equations for exchange, magnetostatic and retarded waves in infinite and semi-infinite ferromagnetic superlattices are derived by the "transfer matrix" (T matrix) method.
Abstract: General dispersion equations for exchange, magnetostatic and retarded waves in infinite and semi-infinite ferromagnetic superlattices are derived by the 'transfer matrix' (T matrix) method. The elementary unit of the superlattices under consideration consists of N different ferromagnetic layers. The equations for bulk waves are expressed through the diagonal elements of the T matrix whereas those for surface waves are expressed through the T matrix and a column matrix D which describes surface boundary conditions. The explicit form of the T and D matrices is given for 'pure' exchange and 'pure' dipolar waves.
82 citations
TL;DR: In this paper, the temperature dependence of the exchange constant between 20°C and 573°C using three previously published data sets from inelastic neutron scattering by spin wave excitations in magnetite was calculated.
Abstract: We calculated the temperature dependence of the exchange constant between 20°C and 573°C using three previously published data sets from inelastic neutron scattering by spin wave excitations in magnetite. The exchange constant in magnetite varies as a function of temperature approximately as the saturation magnetization to the power 1.7. Our synthesis of temperature dependent spin wave dispersion data provides an experimental foundation for the temperature variation of the exchange energy which is critical for micromagnetic domain structure calculations and for an understanding of the acquisition of thermoremanent magnetization in rocks.
TL;DR: Recherche de termes topologiques dans un Lagrangien de champ moyen pour les ferromagnetiques et les antiferromagnetsiques inspiree par le modele de Hubbard.
Abstract: We look for possible topological terms in a mean-field Lagrangian for ferromagnets and antiferromagnets inspired by the Hubbard model and study their physical effects. A topological term corresponding to Berry's phase causes the order parameter to behave like a spin moment. We find that the Hopf term is not induced and thus there is no evidence for a neutral fermion in this theory.
TL;DR: Spin superposition in neutron interferometry, spin measurement, and non-local Einstein-Podolsky-Rosen spin correlations can be understood in terms of well-defined individual particle trajectories with continuously variable spin vectors as mentioned in this paper.
Abstract: Spin superposition in neutron interferometry, spin measurement, and non–local Einstein-Podolsky-Rosen spin correlations can be understood in terms of well–defined individual particle trajectories with continuously variable spin vectors.
TL;DR: Etude de la dependance en temperature de l'aimantation de surface dans le regime onde de spin dans la regime ond de spin.
Abstract: Etude de la dependance en temperature de l'aimantation de surface dans le regime onde de spin
TL;DR: An experimental study is made of the interactions between spin-wave modes excited in a sphere of yttrium iron garnet by pumping the Suhl subsidiary absorption at 9.2 GHz with the dc field parallel to (111) to observe dynamical behavior of the magnetization.
Abstract: An experimental study is made of the interactions between spin-wave modes excited in a sphere of yttrium iron garnet by pumping the Suhl subsidiary absorption at 9.2 GHz with the dc field parallel to [111]. The dynamical behavior of the magnetization is observed under high resolution by varying two control parameters, dc field (580 OelHl2100 Oe) and microwave pump power (1 mWlPl200 mW). Within this parameter space quite varied behavior is found: (i) onset of the Suhl instability by excitation of a single spin-wave mode with very narrow linewidth (l0.5 G); (ii) when two or more modes are excited, interactions lead to auto-oscillations with a systematic dependence of frequency (${10}^{4}$--${10}^{6}$ Hz) on pump power these oscillations displaying period doubling to chaos; (iii) quasiperiodicity, locking, and chaos occur when three or more modes are excited; (iv) abrupt transition to wide-band power spectra (i.e., turbulence), with hysteresis; (v) irregular relaxation oscillations and aperiodic spiking behavior. A theoretical model is developed from first principles, using the plane-wave approximation and including anisotropy effects, obtaining the lowest-order nonlinear interaction terms between the excited modes. Bifurcation behavior is examined, and dynamical behavior is numerically computed and compared to the experimental data, explaining a number of features. A theory is developed regarding the nature of the experimentally observed relaxation oscillations and spiking behavior based on the interaction of ``weak'' and ``strong'' modes, and this is demonstrated in the numerical simulations.
TL;DR: Spin-wave properties have been calculated for multilayered structures consisting of alternating ferromagnetic and nonmagnetic layers, as well as for all-ferromagnetic structures, fully taking into account magnetic interface anisotropies and exchange contributions.
Abstract: Spin-wave properties have been calculated for multilayered structures consisting of alternating ferromagnetic and nonmagnetic layers, as well as for all-ferromagnetic structures, fully taking into account magnetic interface anisotropies and exchange contributions. In the crossing regime of dipolar modes and exchange modes, the gap width is strongly influenced by the amount of interface anisotropy. In the case of all-magnetic multilayered structures, a new type of collective spin-wave excitation arising from coupled exchange modes is predicted.
TL;DR: The theory of long-wavelength spin waves in superlattices which incorporate magnetically ordered films that interact either through dipolar fields generated by spin motions or exchange couplings at interfaces or those mediated by an intervening nonmagnetic film is explored.
Abstract: We explore the theory of long-wavelength spin waves in superlattices which incorporate magnetically ordered films that interact either through dipolar fields generated by spin motions or exchange couplings at interfaces or those mediated by an intervening nonmagnetic film. We show that for long wavelengths one may replace the superlattice by an effective medium described by a permeability tensor composed of those of the constituent films. Our treatment applied to a semi-infinite lattice of ferromagnetic films reproduces results obtained earlier in a full theory by Camley, Rahman, and Mills. We also develop an effective medium theory of Y-Gd superlattices in the anti-phase-domain configuration, with transverse field applied. We obtain a rich spectrum of surface spin waves in this case. We also obtain Green's functions for the average medium description of the Y-Gd system and use these to discuss surface-mode contributions to the spectral densities explored by Brillouin scattering.
TL;DR: In this paper, the behavior of a particular spinwave mode due to spin canting induced by the antiferromagnetic coupling is discussed. But the authors do not discuss the implications of this observation.
Abstract: Thin films of Fe when separated by approximately 8 A of Cr couple antiferromagnetically. Evidence for this comes from spin‐wave‐mode spectra as measured by means of light scattering and hysteresis curves, here obtained by means of the magneto‐optic Kerr effect. Based on new and more‐detailed data we would like to discuss the behavior of a particular spin‐wave mode due to the spin canting induced by the antiferromagnetic coupling. It is related to a Goldstone mode. The experiments also show that antiferromagnetic coupling occurs not only for films grown along [100] but also for films grown along [110]. We discuss the implications of this observation.
TL;DR: In this article, the authors report on the observation and analysis of collective magnetostatic spin-wave excitations in magnetic superlattices and the influence of interface anisotropies, which can become dominant for small modulation wavelengths, is discussed.
Abstract: We report on the observation and the analysis of collective magnetostatic spin‐wave excitations in magnetic superlattices. The influence of interface anisotropies, which can become dominant for small modulation wavelengths, is discussed. For the system Fe/Pd we show that Brillouin spectroscopy experiments in combination with the measurement of the saturation magnetization by a SQUID magnetometer give evidence for a magnetic polarization of the Pd spacer layers, as well as for a small negative out‐of‐plane interface anisotropy constant of Ks =−0.15 erg/cm2.
TL;DR: In this paper, the Backlund transformation was used to construct one-and two-dimensional vortex lattices on a homogeneous and periodic background using the explicit form using Backlund transform, and the interaction of vortex magnetic structures with nonlinear spin waves was considered.
TL;DR: In this paper, the mean amplitude of the normal mode is determined from the requirement that the mean energy stored in the mode be equal to the thermal energy of an oscillator having the same frequency.
TL;DR: In this paper, the general dispersion equations for bulk and surface magnetostatic modes in N-layered superlattices derived in the previous paper by the 'transfer matrix' method, are applied here to the cases of N=2 and N=3 different magnetic layers in an elementary unit.
Abstract: For pt. I, see ibid., vol.21, p.1021 (1988). The general dispersion equations for bulk and surface magnetostatic modes in N-layered superlattices derived in the previous paper by the 'transfer matrix' method, are applied here to the cases of N=2 and N=3 different magnetic layers in an elementary unit. The layers are assumed to be magnetised parallel to the film planes and parallel to one another. Explicit forms of the 'transfer matrix' and of the dispersion equations for bulk and surface modes are given for propagation in the Voigt configuration. Numerical examples of the wave spectrum are presented for some superlattices composed of ferro magnetic, antiferromagnetic and nonmagnetic materials.
TL;DR: In this article, Fe 2 P is of the hexagonal C-22 type structure and exhibits c-axis ferromagnetism below 130 K. In the intermediate range between 130 K and 217 K, the canted ferromagnetic properties with a uniform component along the c -axis M 0 and a staggered component in the c-plane M Q appear, and the first order transition takes place at T c =217 K from the Canted Ferromagnetic to paramagnetic properties, leading to the existence of a giant short range order up to T =3 T c
Abstract: Neutron elastic and inelastic scattering experiments have been performed on Fe 2 P single crystals in the temperature range from 8 K to 800 K. Fe 2 P is of the hexagonal C-22 type structure and exhibits c -axis ferromagnetism below 130 K. In the intermediate range between 130 K and 217 K, the canted ferromagnetism with a uniform component along the c -axis M 0 and a staggered component in the c -plane M Q appears, and the first order transition takes place at T c =217 K from the canted ferromagnetism to paramagnetism. The most interesting behaviour is the existence of giant short range order up to T =3 T c . It originates in the small stiffness constants D and leads to the strong deviation of susceptibility from the Curie-Weiss law. The amplitude of the spin fluctuation observed In Fe 2 P In the pararnagnetic phase is understood by the simple model with parameters deduced from the spin wave dispersion at low temperature, the magnetization and uniform susceptibility.
TL;DR: In this paper, the authors discuss the dynamical response of the two-sublattice, uniaxial Heisenberg antiferromagnet, for the case where an external magnetic field is applied in arbitrary direction relative to the easy axis.
Abstract: We discuss the dynamical response of the two-sublattice, uniaxial Heisenberg antiferromagnet, for the case where an external magnetic field is applied in arbitrary direction relative to the easy axis. For the case where the external field is perpendicular to this axis, we obtain simple expressions for the nonzero elements of the magnetic-susceptibility tensor. These are used to discuss the properties of spin waves on the surface of an antiferromagnet, for the case where both the easy axis and the external magnetic field are parallel to the surface, but mutually perpendicular.
TL;DR: In this article, a new theory of the Brillouin shift in the inelastic scattering of light by magnetostatic spin waves is presented, which treats the magnetic surface anisotropy constants Ks and Kss directly rather than via the stratagem of effective volume anisotropies.
Abstract: A new theory of the Brillouin shift in the inelastic scattering of light by magnetostatic spin waves is presented. Contrary to previous work, the present calculations do include exchange effects and treat the magnetic surface anisotropy constants Ks and Kss directly rather than via the stratagem of effective volume anisotropies. The experimental data for {110} Fe on W are explained about as well by the present theory as by previous work. A detailed analysis reveals the previously unnoticed fact that the signs of Ks and Kss for (110) Fe on W are opposite to those for (110) Fe on GaAs. Some new spin‐wave modes arising from exchange are predicted and shown to occur outside the frequency range which has been investigated experimentally. A quantitative explanation is proposed for the occasional applicability of a theory based on effective volume anisotropies and zero exchange.
TL;DR: Triple-axis neutron spectroscopy has been used to study high-energy magnetic excitations for iron and scattering contours established for the (100) and (111) directions show effects not present in localized-electron models of ferromagnetism.
Abstract: Triple-axis neutron spectroscopy has been used to study high-energy magnetic excitations for iron. The scattering contours established for the (100) and (111) directions show effects not present in localized-electron models of ferromagnetism. Interactions between spin waves and single-particle excitations are clearly seen for both crystallographic directions while two parts to the spin-wave branch are observed for the (100) direction.
TL;DR: In this paper, the authors investigated the TE-to-TM optical mode conversion that takes place when magnetostatic waves (MSW) and a guided light beam propagate collinearly in an yttrium-iron-garnet (YIG) film.
Abstract: The TE-to-TM optical mode conversion that takes place when magnetostatic waves (MSW) and a guided light beam propagate collinearly in an yttrium-iron-garnet (YIG) film is investigated. The experimental results show unexpectedly high intensity and broad bandwidth when microwave power levels on the order of 35 dBm are used. This effect is clearly nonlinear, and it is speculated that it could be due to spin wave excitation or to high transducer current effects. The experiments were carried out between 4 and 7 GHz using 1.3- mu m radiation. >