Nuclear magnetic moment of 57Cu ground state

The nuclear magnetic moment of the ground state of ⁵⁷Cu(I^π = 3/2^-, T_1/2 = 196.3 ms) has been measured to be |μ(⁵⁷Cu)| = (2.00 ±0.05) μ_N using the β-NMR technique. Together with the known magnetic moment of the mirror partner ⁵⁷Ni, the spin expectation value was extracted as = -0.78 ± 0.13. Discrepancy between present results and shell model calculations in the full fp shell implies significant shell breaking at ⁵⁶Ni with the neutron number N = 28.     

The ground state of the exciton in a magnetic field

The ground state of the isotropic exciton in a magnetic field has been computed exactly for several values of the magnetic field in the weak, medium and strong regions. Together with an outline of the method adopted, values of the energy and of the oscillator strength are reported.     

Surface excitations in magnetic systems with a singlet ground state

We have investigated surface excitations in a system wherein the ionic ground state is a magnetic singlet. The pseudospin formalism is employed to account for the crystal-field and exchange interactions between the ions in a Heisenberg ferromagnet with the singlet-triplet crystal-field-only level scheme. The Hamiltonian was studied in the molecular field approximation to find the possible ground states. Surface excitations for the simple cubic structure were investigated for the (001) surface in the random phase approximation. Analytic expressions have been obtained for the thermodynamic Green functions. For a fully magnetized molecular field ground state, there are in general two bulk bands, the spin-wave and the excitonic. Surface modes were found to exist below the spin-wave band, above the excitonic band and between the bands. The dispersion curves can exist only over one or two limited regions of the two-dimensional wave-vector parallel to the crystal surface.     

Nuclear magnetic moment of the 57Cu ground state

The nuclear magnetic moment of the ground state of (57)Cu(Iota(pi) = 3/2(-), T(1/2) = 196.3 ms) has been measured to be /mu((57)Cu)/ = (2.00 +/- 0.05)mu(N) using the beta-NMR technique. Together with the known magnetic moment of the mirror partner (57)Ni, the spin expectation value was extracted as = -0.078 +/- 0.13. This is the heaviest isospin mirror T = 1/2 pair above the (40)Ca region for which both ground state magnetic moments have been determined. The discrepancy between the present results and shell-model calculations in the full f p shell giving mu((57)Cu) approximately 2.4mu(N) and approximately 0.5 implies significant shell breaking at (56)Ni with the neutron number N = 28.     

Controlling the magnetic ground state in Cr1-x Vx films

We demonstrate the ability to control the magnetic phase diagram of Cr1-x Vx(110) thin films grown on a W(110) substrate. Using angle-resolved photoemission, we have mapped paramagnetic and commensurate and incommensurate antiferromagnetic phases as a function of temperature, film thickness, and composition. We show that surface-localized electron states play a key role in the observed phase behaviors and suggest from this that it might be possible to control the magnetic phase by applying an external electric field.     

Zeeman effect on magnetic susceptibility in singlet ground state PrNi5

The Zeeman effect on the crystal electric field (CEF) magnetic susceptibility in 4f-electron singlet ground state (SGS) systems is studied analytically in the framework of the molecular-field model and experimentally by measuring the magnetic susceptibility of SGS compound PrNi₅. The most striking result of the analysis is the shift of the zero-field magnetic susceptibility maximum to lower temperatures in magnetic field. This thoroughly CEF effect is a direct consequence of the convergence of the SGS and the low lying Zeeman branch of the first excited state in an applied magnetic field. The observed shift of the susceptibility maximum from 14 K to 9 K in polycrystalline PrNi₅ by applying a magnetic field of 9T confirms the foregone conclusion.     

The ground state of two-dimensional electrons in a nonuniform magnetic field

An exact solution to the Schrödinger equation for the ground state of two-dimensional Pauli electrons in a nonuniform transverse magnetic field H is presented for two cases. In the first case, the field H depends on a single variable, H = H(y), while in the second case, the field is axially symmetric, H = H(ρ), ρ²=x ²+y ². The electron density distributions n = n(y) and n = n(ρ) that correspond to a completely filled lower level are found. For quasiuniform fields of fixed sign, the functions n(y) and n(ρ) are locally related to the magnetic field: n(y) = H(y)/?₀ and n(ρ) = H(ρ)/?₀, where ?₀ = hc/|e| is a magnetic flux quantum. Magnetic fields are considered that are periodic, singular, and bounded in the plane xy. Finite electron objects in a nonuniform magnetic field are analyzed.     

Ortho-para splitting of the exciton ground state in a strong magnetic field

Exciton spectra in bulk semiconductor in strong magnetic fields were studied in the two-band Dirac model. An expression for the energy of ortho-para splitting of the ground state was derived.     

Singlet ground state magnetism: II. magnetic excitons in paramagnetic TbP

The magnetic ₁ – ₄ exciton of the singlet ground state system TbP has been studied by inelastic neutron scattering above the antiferromagnetic ordering temperature. Considerable dispersion and a pronounced splitting was found in the [100] and [110] directions. Both the band width and the splitting increased rapidly as the transition temperature was approached in accordance with the predictions of the RPA-theory. The dispersion is analysed in terms of a phenomenological model using interactions up to the fourth nearest neighbour.Work supported by the BMFT     

Magnetic phase transition and magnetic structure of ground state in CsDyW O

Magnetic phase transition in the CsDyW₂O₈ magnet has been studied by means of low temperature specific heat C ( T ) measurements. The magnetic ordering temperature of the Dy³⁺ sublattice was established to be 1.34 K. The experimental results indicate on the antiferromagnetic character of interactions between Dy³⁺ ions. The behavior of the C ( T ) dependencies above and below T _N is discussed in frames of different theoretical models. The measurements data on temperature and field dependencies of magnetization are used to calculate the exchange and dipole-dipole interactions energy and to determine the possible magnetic structure of the ground state. Received 7 January 2002 / Received in final form 15 May 2002 Published online 7 September 2002     

Density of states in the magnetic ground state of the Friedel-Anderson impurity

By applying a magnetic field whose Zeeman energy exceeds the Kondo energy by an order of magnitude the ground state of the Friedel-Anderson impurity is a magnetic state. In recent years the author introduced the FAIR (Friedel Artificially Inserted Resonance) method to investigate the impurity properties. Within this FAIR approach the full excitation spectrum and the composition of the excitations is calculated and numerically evaluated. From the excitation spectrum the electron density of states is calculated. Majority and minority d-resonances are obtained. The width of the resonances is about twice as wide as the mean field theory predicts. This broadening reduces the height of the resonance curve and therefore the density of states by a factor of two. This yields an intuitive understanding for a previous result of the FAIR approach that it requires a much larger Coulomb interaction for the formation of a magnetic moment than the mean field theory.     

Fragile magnetic ground state in half-doped LaSr2Mn2O7

We investigated the orbital and antiferromagnetic ordering behaviors of the half-doped bilayer manganite La(2-2x)Sr(1+2x)Mn2O7 (x ? 0.5) by using Mn L(2,3)-edge resonant soft x-ray scattering. Resonant soft x-ray scattering reveals the CE-type orbital order below T(oo) ? 220 K, which shows partial melting behavior below T(m) ? 165 K. We also found coexistence CE- and A-type antiferromagnetic orders. Both orders involve the CE-type orbital order with nearly the same orbital character and are coupled with each other. These results manifest that the ground state with the CE-type antiferromagnetic order is easily susceptible to destabilization into the A-type one even with a small fluctuation of the doping level, as suggested by the extremely narrow magnetic phase boundaries at x ? 0.5±0.005.     

On the magnetic dipole moment of the153Tb ground state

Temperature dependence of the angular distribution anisotropy of the 212·0 keV gamma-ray following the decay of¹⁵³Tb oriented in a gadolinium host was measured at temperatures from 16 to 70 mK. Magnetic dipole hyperfine splitting parameter a₀ for¹⁵³Tb(Gd) and magnetic dipole moment of the¹⁵³Tb ground state were estimated to be ¦a ₀¦1·2×10^–5 eV and ¦¦3·1 nuclear magnetons, respectively.Authors are indebted to Dr. N. A. Lebedev, Yu. V. Yushkewich and the staff of the JINR synchrocyclotron for the preparation of the¹⁵³Tb activity. The participation of Ing. L. Mare, J. Ferencei and S. I. Antonov in the measurements is also acknowledged.     

On the theory of superconductors with magnetic impurities in a singlet ground state

We attempt a theoretical axplanation of recent measurements of Bucher et al. on superconducting systems containing rare earth impurities in a single ground state and propose an additional experiment to demonstrate the importance of crystalline fields.     

Calculation of the magnetic hyperfine structure in the ground electronic state of HCCO

In this paper we analyze the spin-spin hyperfine interaction in the two components of the ground electronic state of the free π radical HCCO, A²A′[²Π] and X²A″. Electronic mean values of the Fermi contact constants of all magnetic nuclei [¹H, ¹³C₁, ¹³C₂,¹⁷O] are calculated using models that include the electron-correlation correction, primarily CCSD method in the cc-pwCVTZ basis set and B3LYP functional in the cc-pCVQZ basis set. Also, we have calculated components of the anisotropic hyperfine tensor for the ground X²A″ state. The dependence of hyperfine coupling constants (HFCCs) on the two bending coordinates is examined, and the results of HCC bending (vibrational) averaging of electronic mean values are presented for both states. It is demonstrated that electronic and subsequent vibrational averaging of the HFCCs suffices for obtaining results that are in good agreement with available experimental findings (for proton) in the X²A″ state, owing to a small geometry dependence of these quantities, and relatively distant minimum from linearity.     

The ground state of a strongly correlated fermion system in a magnetic field

A new variational method is used to investigate the ground state of the Hubbard model with a half-filled band for a one-dimensional chain, a planar square lattice, and a simple cubic lattice. A metamagnetic transition is found to occur in a one-dimensional chain and a simple square lattice. A simple cubic lattice does not undergo the metamagnetic transition.