Showing papers on "Exchange interaction published in 1985"
TL;DR: In this article, large dc current pulses, ≂2 μs long, are sent through 30-40nm-thick Ni87Fe13 films containing Neel walls, and wall displacements are seen for current densities ≥ 1.2×107 A/cm2.
Abstract: Large dc current pulses, ≂2 μs long, are sent through 30–40‐nm‐thick Ni87Fe13 films containing Neel walls. Wall displacements are seen for current densities ≥1.2×107 A/cm2. Displacements reverse when current sense is reversed. Walls always move in direction of charge carriers in this electronlike material. Our results agree with a theory of s‐d exchange interaction between walls and 4s conduction electrons. Hydromagnetic ‘‘domain‐drag’’ forces are too small in such very thin films to explain our data.
148 citations
TL;DR: In this paper, the hierarchy of Mn-Mn exchange mechanisms in Cd 1− x Mn x Te and related alloys is calculated perturbatively using a generalized Anderson Hamiltonian.
100 citations
TL;DR: In this article, the Curie temperature of ferromagnetic metals in the mean field approximations is derived for arbitrary types of exchange interactions, and an exact formula for the effective exchange parameter J0 is derived.
76 citations
TL;DR: In this article, the authors studied the spin-wave modes in magnetic multilayers and found that the amount of exchange can be tailored by choosing the proper materials or thickness for the nonmagnetic intermediate layers between the magnetic films.
Abstract: Spin‐wave modes in magnetic multilayers are of interest both for basic research and for application—for example, in microwave devices. Here I would like to discuss some ways to manipulate the mode spectra of such multilayers. One way, for example, would be to have reversed magnetization direction in adjacent layers which can be achieved by tailoring the coercive forces of the films in a proper way. The mode spectrum of such a system has been derived only recently and I would like to report a few important results. Also I would like to discuss the case where the films are coupled by exchange as well as by the dipolar interaction which is always there. Here the amount of exchange can be tailored by choosing the proper materials or thickness for the nonmagnetic intermediate layers between the magnetic films. We have studied these effects for a couple of Fe sandwiches with intermediate layers of various materials and find a short coupling length (<5 A) for V and Cr, and a long one (≲20 A) for Cu, Ag, Au, and ...
73 citations
TL;DR: Premiere caracterisation complete experimentale des processus de diffusion elastique et inelastique a deux electrons dans un ferromagnetique islamique.
Abstract: Premiere caracterisation complete experimentale des processus de diffusion elastique et inelastique a deux electrons dans un ferromagnetique
71 citations
TL;DR: In this paper, the temperature dependence of the Gd magnetization is deduced from the exchange interactions between Gd and Fe spins, and the main axis of the electric field gradient is shown to have different directions at the two rare earth sites.
70 citations
68 citations
TL;DR: In this paper, a theory for calculating the crystal field effects in Kondo systems of Ce compounds and alloys is presented, where the static and dynamical susceptibilities are formulated as functions of the self-energy of the pseudofermions.
Abstract: We present a theory for calculating the crystal field effects in Kondo systems of Ce compounds and alloys. By extending Abrikosov's pseudofermion method, the static and dynamical susceptibilities are formulated as functions of the self-energy of the pseudofermions. The self-energy is self-consistently treated in the ladder approximation. It is shown that the crystal field is not constant but depends on temperature through the renormalization of the exchange interaction between Ce 3+ ions and conduction electrons. The neutron quasi-elastic and inelastic scattering spectra and the static susceptibility are in good agreement with the experimental ones in the cubic Kondo system, Ce x La 1- x Al 2 . This agreement suggests that the present theory is applicable to many materials.
62 citations
TL;DR: In this paper, it is shown that the low temperature phase II is an antiferromagnetic state of orbital spins caused by the exchange interaction, which can explain various mysterious experimental results of phase II such as the increase of the transition temperature with increasing magnetic fields, which vanish in the absence of fields.
Abstract: It is definite from recent theoretical and experimnental works that a quartet \(\varGamma_{8}\) is the ground multiplet of f levels in CeB 6 Because the degeneracy of the quartet is composed of the orbital degeneracy as well as the Kramers degeneracy, its degree of freedom can be expressed by two kinds of Pauli matrices, which are called orbital spins and magnetic spins, respectively It is proposed that the low temperature phase II is an antiferromagnetic state of orbital spins caused by the exchange interaction Our model can explain various mysterious experimental results of phase II such as the increase of the transition temperature with increasing magnetic fields and the appearance of antiferromagnetic motments in the presence of fields, which vanish in the absence of fields Therefore it can be concluded that the ordering in phase II of CeB 6 is the first example of the orbital ordering realized by the exchange interaction
57 citations
TL;DR: Mesures d'effet Mossbauer 57 Fe, de diffraction RX et de susceptibilite magnetique, entre 4,2 and 900 K, sur SrFeO 3−y pour 0,15
Abstract: Mesures d'effet Mossbauer 57 Fe, de diffraction RX et de susceptibilite magnetique, entre 4,2 et 900 K, sur SrFeO 3−y pour 0,15
56 citations
TL;DR: This new approach to the Ni photoemission problem yields accurately the experimental bandwidth, exchange splitting, satellite position, and relative intensities, and physical conclusions about the true Ni many-body states are drawn.
Abstract: Exact calculated results for the nickel density of electron states, as would be measured in valence-band photoemission, are presented. A realistic local-density-approximation one-electron structure, sampled at four wave vectors, and an intrasite electron-electron interaction of full generality are used. This new approach to the Ni photoemission problem yields accurately the experimental bandwidth, exchange splitting, satellite position, and relative intensities. Physical conclusions about the true Ni many-body states are drawn.
TL;DR: In this paper, the critical behavior of a spin-one Ising model with biquadratic exchange interactions was studied using the mean field renormalization group method, and the phase diagram for various lattices was obtained.
TL;DR: In this paper, the ESR line shifts for paramagnetic particles have been analyzed in detail as associated with a finite encounter time and the spin precession at a moment of encounter.
TL;DR: In this paper, a new formula for the spin-wave stiffness constant D was derived and compared with previous work, and it was shown that in NiD is very sensitive to the 'ground-state' exchange splitting Delta in the d band and that hybridisation with the sp band has little effect on D.
Abstract: A new formula is derived for the spin-wave stiffness constant D and is compared with previous work. It is shown that in NiD is very sensitive to the 'ground-state' exchange splitting Delta in the d band and that hybridisation with the sp band has little effect on D. The observed value of D yields a value of 0.40 eV for Delta , which is larger than the observed quasiparticle exchange splitting of 0.33 eV, as expected theoretically. Calculations on D in Ni alloys, within the virtual crystal approximation, are compared with experimental results on NiCo and NiFe.
TL;DR: In this article, the transition fields that have been observed in the basal-plane magnetisation curves of Ho 2 Co 17 can successfully be described in a two-sublattice model and provide a direct method to evaluate the molecular field acting on the holmium moment.
TL;DR: Vibrationally elastic scattering over the energy range 0.0006--11.6 eV is reported and the ..sigma.. symmetry was found to be very sensitive to the treatment of exchange and to the effect of polarization.
Abstract: We report results for vibrationally elastic scattering over the energy range 0.0006--11.6 eV. The interaction potential is composed of a near-Hartree-Fock static term plus a parameter-free model of the correlation-polarization potential. The exchange interaction is included exactly through a separable expansion. Results with a model-exchange potential (free-electron-gas plus orthogonalization) are also reported. A resonance appears in Pi symmetry near 2.7 eV (width 1.9 eV) that may be the same feature observed in several experiments. In the model-exchange calculation the Pi resonance is shifted toward higher energy (3.8 eV, width 2.4 eV). The ..sigma.. symmetry was also found to be very sensitive to the treatment of exchange and to the effect of polarization. Differential and rotational excitation cross sections are evaluated in the multipole-extracted adiabatic-nuclei approximation. Results are compared with the available experimental and theoretical data.
TL;DR: In this article, the elastic softening of (C 11 −C 12 ) 2 and C 44 in CeB 6 and Ce 0.5 La0.5 B 6 are explained by the strain susceptibility with a Г 8 (0 K)−Г 7 (545 K) level scheme including the quadrupolar exchange interaction.
TL;DR: In this article, magnetic susceptibility and magnetization studies on the linear chain chromium(III) compounds catena-fluorophthalocyaninatochromium (III), CrPcFn, CrPcanCNn, Catena-cyanophthalocalocalocyanine (Chen-Cyanophthoric-linearin-closine) (Cyanin-Cylindrical-Linear-Closine), CrpcCNn (CrPcNcln), and CrPncFn
Abstract: : Magnetic susceptibility and magnetization studies on the linear chain chromium(III) compounds catena-fluorophthalocyaninatochromium(III), CrPcF n, and catena-cyanophthalocyaninatochromium (III), CrPcCNn, reveal that the chromium (III) ions in CrPcFn and CrPcCNn are magnetically exchange coupled. The magnetic susceptibility data for CrPcFn may be fit with Heisenberg linear chain theory for antiferromagnetic exchange with J = -12.2/cm and g = 2.00. The magnetic susceptiblity data for CrPcCNn may be fit with Heisenberg linear chain theory for ferromagnetic exchange with J = 0.2/cm and g = 1.98. CrPcCNn provides the first example of ferromagnetic exchange in a linear chain of chromium (III) ions. The difference in the exchange interactions in CrPcFn and CrPcCNn may be understood in terms of the electronegativities of the bridges and in terms of the orbitals which transmit the superexchange interactions. Originator supplied keywords include: Electrical conductivity (phthalocyanine); Low-dimensional conducting materials.
TL;DR: It is found that the impurity minority-spin states are quite wide and lie close to the Fermi level, which raises questions concerning the validity of the use of a Kondo Hamiltonian to determine the low-energy scale properties.
Abstract: Various electron-spectroscopy techniques are used to determine the electronic structure of Mn impurities in Ag and Cu. The spectral distributions of both minority- and majority-spin impurity d states are determined experimentally and compared to model calculations considering the photoemission matrix elements. The exchange and Coulomb integrals and energetic positions of the impurity d states as well as the impurity-host d-s and d-d hybridizations are determined. We find that the impurity minority-spin states are quite wide and lie close to the Fermi level, which raises questions concerning the validity of the use of a Kondo Hamiltonian to determine the low-energy scale properties. In addition, the hybridization of the majority-spin states with the host d band is larger, causing these to delocalize, whereas the magnetic moment remains localized. This large hybridization can introduce new exchange mechanisms not foreseen in conventional models.
TL;DR: In this paper, the parameters involved in quantum theories of electron transfer processes are expressed in terms of orbital integrals for the case of biological molecules coupled by an exchange interaction, and conditions where T ab L related to the exchange parameter J are discussed.
TL;DR: In this paper, the spin-coupled VB theory is applied to the dipole moment function of LiH(X 1 Σ + ) and a series of calculations is reported (1, 78, 127 and 188 spatial configurations) which demonstrates the rapid convergence of this property onto that given by accurate MO CI wavefunctions.
TL;DR: Inelastic neutron scattering measurements on MnP reveal that the spin wave gap vanishes at the paramagnetic-ferromagnetic phase boundary in a manner predicted by the transverse field Ising model as mentioned in this paper.
Abstract: Inelastic neutron scattering measurements on MnP reveal that the spin wave gap vanishes at the paramagnetic-ferromagnetic phase boundary in a manner predicted by the transverse field Ising model. The occurrence of the tricritical point in a temperature-field phase diagram is strongly related to the temperature-driven change of the phenomenological parameter P ≡ J 2 z / J 1 z which describes the competition between the effective nearest and next-nearest-neighbor exchange interactions. The itinerant nature of the magnetism of this compound is emphasized as a possible origin of the temperature dependence of P . The tricritical point is most likely a Lifshitz Point as pointed out in detailed measurements of the phase diagram by Shapira et al.
TL;DR: In this article, the magnetic properties of bimetallic ferrimagnetic chains in CoNi(EDTA)6H2O were investigated in terms of the Heisenberg model with an exchange coupling J=−7.5 K.
Abstract: We report on the magnetic behavior of ‘‘rigid’’ ferrimagnetic chains isolated in bimetallic complexes of the EDTA and ‘‘flexible’’ ones obtained in the amorphous variety. As shown by LAXS, the only noteworthy difference in the amorphous state is the random distribution of bond angles between nearest neighbors within chains. The ‘‘rigid’’ bimetallic chains in CoNi(EDTA)6H2O are described in terms of Heisenberg model with an exchange coupling J=−7.5 K. The behavior of the amorphous variety somewhat differs, following the law X=AT−0.8 typical of REHAC. A classical spin chain model involving a J distribution and alternating g factors allows to explain successfully the temperature dependence of the susceptibility.
TL;DR: In this paper, the random anisotropy (D) and exchange (J) constants in amorphous Dy x Gd 1− x Ni have been obtained from an analysis of the measured magnetization curves in terms of the H.P.Z. model.
TL;DR: In this paper, the role of a biquadratic exchange interaction in the solitary-wave solutions of the continuum anistropic Heisenberg ferromagnetic chain is discussed using coherent states.
Abstract: The role of a biquadratic exchange interaction in the solitary-wave solutions of the continuum anistropic Heisenberg ferromagnetic chain is discussed using coherent states. Existence of solitons with energies smaller than those corresponding to spin waves modes is predicted.
TL;DR: In this paper, the Shubnikov-deHaas effect was used to measure the spin g-factor for two-dimensional electron gas in GaAs and the effect was attributed to the exchange interaction and compared with the theory of Ando and Uemura.
TL;DR: In this paper, a continuous integration method is used for the investigation of the Heisenberg quantum model with structure disorder, and the free energy of such system is obtained as the perturbation theory series of the inverse cube of effective exchange interaction radius for arbitrary temperature and spin value.
Abstract: A continuous integration method is used for the investigation of the Heisenberg quantum model with structure disorder. The free energy of such system is obtained as the perturbation theory series of the inverse cube of effective exchange interaction radius for arbitrary temperature and spin value. The contribution of magnetic and structure fluctuation effects to the thermodynamics, magnetization of the system, and temperature of the ferromagnetic phase transition is investigated. Numerical calculations on the base of model systems show that the change of critical temperature and low temperature magnetization at the amorphization of a crystal are in qualitative agreement with experimental results.
[Russian Text Ignored].
TL;DR: In this paper, the predictions of an effective field treatment of an arbitrary spin Ising model with a Gaussian distribution of exchange coupling strengths, with emphasis on the region j, were presented.