Hyperfine structure in optical spectra of LiYF4-Ho

We report high resolution infrared absorption spectra of LiYF₄-Ho exhibiting well resolved nuclear hyperfine structure (hfs). The halfwidths of some hfs components do not exceed 0.03 cm^?1. Magnetic field at the nucleus is evaluated. Non-radiative relaxation rates due to phonon emission are estimated. With the help of experimentally found 〈Γ₃|J_z|Γ₃〉 matrix elements g-factors of the excited crystal field levels are calculated. Some hfs peculiarities are discussed.     

Further studies in aesthetic field theory VI: The lorentz group

In studying Γ _jk;l ⁱ = 0,g _ij;k = 0 field theory we require that the underlying structure (Γ _βγ ^α ,g _αβ ) be invariant underL (4), the four-dimensional Lorentz group. This can be accommodated into the theory by increasing the dimension to five. In our computer studies we still found a turnabout point forg ₄₄ on running down thex-axis, suggesting that this group may be consistent with a bounded particle. However, with still longer runs down thex-axis, there was some indication that a singularity may be developing.     

31P and1H powder ENDOR study of ozonide radicals in carbonated apatites,synthesized from aqueous solutions

An O ₃ ^? defect in Na⁺ CO ₃ ^2? containing apatite powder has been investigated with ENDOR after X-irradiation. The powder, synthesized by a hydrolysis of octo-calciumphosphate (OCP) and Na₂CO₃ was dried at 25°C until constant weight was reached. At low temperatures, both³¹P and¹H ENDOR spectra were recorded for different settings of the magnetic field (i.e., when the magnetic field is swept through the EPR O ₃ ^? spectrum). The ENDOR powder spectra were thoroughly analyzed using computer simulations based on the “orientation selection principle”. Interactions with two types of protons and two types of³¹P nuclei could be resolved. In this way, a detailed model could be established for the O ₃ ^? ion in the hydroxyapatite lattice. The defect is located between two successive vacant hydroxyl sites. The axis connecting the two outer oxygen atoms (g _y-axis) of the O ₃ ^? ion is found to be along the hexagonalc-axis of the lattice. The twofold axis of the defect ion (g _z-axis) is parallel to theb-axis of the lattice.     

Magnetopolaritons in ZnTe

From an invariant expansion, we construct the exciton Hamiltonian for the Γ₆×Γ₈ excitons in theT _d -type material ZnTe represented by an 8×8 matrix including the influences of a finite wave vector and an external magnetic field. We diagonalize the Hamiltonian matrix to obtain the exciton states. Then the excitons are coupled to the electromagnetic radiation field thus giving the polariton states. The theoretical dispersion curves are fitted to the results of two-photon Raman scattering and reflection experiments in magnetic fields up to 22 T. From this fit we deduce precise values for the eigenergies, exciton masses,g-factors, and diamagnetic shifts.     

Mesoscopic spin-flip transport through a hybrid system with a single molecular dot system applied with ac magnetic fields

We have investigated the current for the system of vibrating quantum dot irradiated with a rotating magnetic field and an oscillating magnetic field by nonequilibrium Green's function. The rotating magnetic field rotates with the angular frequency ωr around the z-axis with the tilt angle ?, and the time-oscillating magnetic field is located in the z-axis with the angular frequency ω. Different behaviors have been shown in the presence of electron-phonon interaction (EPI) which plays a significant role in the transport. The current displays asymmetric behavior as the source-drain bias eV=0, novel side peaks or shoulders can be found due to the phonon absorption and emission procedure, and the negative differential resistance becomes stronger as the parameter g increases. Furthermore, the strong EPI also destroys the quasiperiodic oscillations of current in the region μ₀B₁>2.5Δ. The electron transport properties are also significantly influenced by the linewidth function Γ.     

g-factors of the ground state rotational band of158Dy

Theg-factors of the four lowest states of the ground state rotational band of¹⁵⁸Dy have been determined asg(2 ₁ ⁺ )=+0.362(23),g(4 ₁ ^su+ )=+0.340(20),g(6 ₁ ^su+ )=+0.207(36) andg(8 ₁ ^su+ )=+0.21(11). Theg-factors of the 2⁺ and 4⁺ states were measured by the IPAC method with radioactive samples of 2.4 h¹⁵⁸Er in external magnetic fields. To investigate the higher states, for the first time an on-line γ—γ IPAC experiment was performed with the reaction¹⁵⁶Gd(α, 2n)¹⁵⁸Dy by use of the static hyperfine field of DyGd.     

Etude par effet Mössbauer de la briartite (Cu2FeGeS4)

Mössbauer experiments on Cu₂FeGeS₄ have shown that the ground orbital level of the Fe²⁺ ions is |L_z=0>, which corresponds to the existence of an easy plane of magnetization perpendicular to the tetragonal axis 0z; in the antiferromagnetic phase the magnetic moments actually lie inside this plane. The tetragonal splitting of the ground orbital doublet ₃ is found to be about 1430 cm^?1, and the Néel temperature is 12,3±0,3 K. A. self consistent calculation of molecular field is used to explain the order of magnitude of the hyperfine field observed at low temperature (H_hf=167±2 kOe at 4,2 K).     

Gyromagnetic ratios of 4+ and 6+ states in156Gd and158Gd

The followingg-factors have been derived from time integral measurements of γ-γ angular correlations in the static magnetic hyperfine field of magnetized gadolinium metal probes:¹⁵⁶Gd:g(4 ₁ ⁺ )=+0.310(19)g(6 ₁ ⁺ )=+0.25(21)g(4 ₃ ⁺ , 1511 keV)=+0.809(27)¹⁵⁸Gd:g(4 ₁ ⁺ )=+0.409(15). The 5.35d ¹⁵⁶Tb sources were produced by the reaction¹⁵⁶Gd(d, 2n)¹⁵⁶Tb in our cyclotron. A carrier-free 150y ¹⁵⁸Tb source was obtained from ISOLDE/CERN. In comparison with the precisely knowng-factors of the 2 ₁ ⁺ states,g(2 ₁ ^su+ ,¹⁵⁶Gd) =+0.386(4) andg(2 ₁ ⁺ ,¹⁵⁸Gd)=0.381(4), we observe a large reduction for the¹⁵⁶Gd 4 ₁ ⁺ state whereasg increases slightly for¹⁵⁸Gd. The half-life of the 4 ₁ ⁺ state of¹⁵⁸Gd was remeasured as¹⁵⁸Gd:T _1/2(4 ₁ ⁺ )=148(2) ps. A measurement of the rotation in the 4 ₃ ⁺ state of¹⁵⁶Gd in external magnetic fields of various strengths up toB _ext=9.5 T did not confirm the anomalous dependence of the magnetic hyperfine field in gadolinium metal on the external field, which has been reported by Persson et al. [29].     

Magnetism and electronic properties of BiFeO3 under lower pressure

Ab initio calculations show an antiferromagnetic-ferromagnetic phase transition around 9-10 GPa and a magnetic anomaly at 12 GPa in BiFeO₃. The magnetic phase transition also involves a structural and insulator-metal transition. The G-type AFM configuration under pressure leads to an increase of the y component and a decrease of the z component of the magnetization, which is caused by the splitting of the d_z² orbital from doubly degenerate e_g states. Our results agree with the recent experimental results.     

Optical absorption due to paraexciton of Cu2O

In Cu₂O a new absorption line is observed at 97 cm^?1 below the n =1 of the yellow exciton (triply degenerate orthoexciton) under a strong magnetic field at 4.2 K. The line is assigned as a transition to a nondegenerate spin triplet state Γ⁺₂ (paraexciton). An analysis including the effects due to the n =1 of the green exciton yields 364 cm^?1 as the exchange energy, and 2.68 and ?1.02, or 1.02 and ?2.68 as the g-factors of the conduction and valence bands forming the yellow exciton.     

Non-spherical magnetic moment in MnAlGe

The magnetic structure factors of MnAlGe (space groupP4/nmm) measured with polarised neutrons have been expressed in terms of the magnetic moment of the Mn atom (site symmetry tetrahedral with tetragonal distortion), the Bessel transforms 〈j _n〉 of the Mn radial functions and the fractional occupancies of the moment density in the various crystal field orbitals. The measured structure factors were least-squares fitted with the theoretical expression involving 〈j _n〉 appropriate to the Mn⁰, Mn⁺ and Mn²⁺ atoms. The best fit was got using Mn⁰ transforms, yielding 1·45µ _B as the Mn magnetic moment. The fractional occupancies of the moment density in the crystal field orbitalsA _1g,B _1g E _g andB _2g were obtained. This analysis shows the magnetic moment to be highly non-spherical with a large fractional occupancy (38%) in theA _1g orbital directed along the tetragonal axis while the fractional occupancies ofB _1g andB _2g are found to be 31% and 30% respectively. The fractional occupancy of the moment in theE _g orbital directed towards the Ge and Al atoms is very low (1%). The spatially averaged moment density of Mn in MnAlGe is more diffuse than that of Mn I and Mn II in isostructural Mn₂Sb.     

g-factors of the lowest 2+ and 4+ states in198, 200, 202Hg

Theg-factors of the 2 ₁ ⁺ and 4 ₁ ⁺ states in^198,200,202Hg were simultaneously measured by means of the transient-field perturbed angular correlation method in Coulomb excitation using multi-isotopic targets and thin polarized Gd foils as ferromagnetic host. Theg(2 ₁ ⁺ ) andg(4 ₁ ⁺ ) were found identical within errors in^{198, 200}Hg, while in²⁰⁰Hg lowerg-factor values have been determined. The experimentalg-factors were compared with the predictions of the pairing-plus-quadrupole, dynamical deformation and interacting boson models.     

Magnetic phase diagrams of manganites in the electron doping region

The paper reviews the physical properties of the R_1?xA_xMnO₃ manganites (R=La, Pr, Nd, Sm, etc., A=Ca, Sr, Ba) in the region of their electron doping where the divalent atom concentration x in the compound lies in the interval 0.5<x<1.0. Experimental magnetic phase diagrams of the most well-studied compounds and the results of theoretical calculations of these diagrams made in the tight-binding approximation within the degenerate double-exchange model for T=0 are presented. The experimental section of the review deals primarily with neutron diffraction studies of the magnetic and crystal structures of the manganites, and the theoretical part, with the relation between their magnetic and orbital structures. The review describes, in considerable detail, the method of calculation of the energy spectrum ?(k) and of the total carrier energy for all possible magnetic and orbital configurations of the system corresponding to the translation symmetry of the lattice. The theoretical analysis is carried out separately for two models of the crystal structure, with two and four manganese atoms in the unit cell. All equilibrium magnetic and orbital configurations of the four-sublattice manganite model were determined by minimizing the total energy of the system with respect to the directions of the local manganese magnetic moments and orbital states of the e_g electrons. It is shown that, by using the effective Hamiltonian of the degenerate double-exchange model for the e_g electrons, which takes into account the e_g level splitting, and the Heisenberg Hamiltonian of the localized t_2g electrons, one can describe the diversity of the magnetic phases, the sequence of their alternation with increasing x, and the correlation between the spin and orbital degrees of freedom, which are observed in most electron-doped manganites.     

High precision measurements of theg J-factors of the alkalis using the atomic beam magnetic resonance method

Theg _J-factors of Li⁶, Li⁷, Na²³, Rb⁸⁵, Rb⁸⁷ and Cs¹³³ in their² S _1/2 ground states have been measured relative to theg _J-factor of K³⁹ with a precision of a few parts in 10⁷ using the atomic beam magnetic resonance method.     

Parameterization of the spectra of configurations 3<Emphasis Type="Italic">p</Emphasis>4<Emphasis Type="Italic">f</Emphasis> and 3<Emphasis Type="Italic">p</Emphasis>5<Emphasis Type="Italic">f</Emphasis> of a phosphorus ion P II. Gyromagnetic ratios

In the one-configuration approximation, in the formalism of irreducible tensor operators, and in the intermediate (real) coupling scheme, numerical values of the fine-structure parameters are determined for the 3p4f and 3p5f highly excited configurations of the P II phosphorus ion with the energy-operator matrix in the LK-coupling approximation. With these values of the fine-structure parameters, the energy-operator matrix is numerically diagonalized in the LS-coupling approximation. The gyromagnetic ratios calculated in both basis sets in the absence of a field are compared with one another, as well as with their vector counterparts and the experimental g-factors available for the 3p4f configuration. The experimental and theoretical g-factors calculated with the LS basis set are in good agreement with the sole exception of the ³ F ₂ level. Note that the calculation of g-factors from the Zeeman splitting in the linear region totally confirmed their agreement with the values calculated in the LS basis set (g _LS ) in the absence of a field. The gyromagnetic ratios are the main objectives of this and previous papers, especially for configurations for which experimental data are absent. Apart from the g-factors, the specific features of Zeeman splitting (the crossings and anticrossings of magnetic components) in the 3p5f configurations were determined. These data are to be compared with results of future experiments. Comparison of gyromagnetic ratios calculated in the intermediate coupling scheme with their vector counterparts showed that most levels of the configurations studied are closer than in the LK-coupling scheme.     

Antiferromagnetic transition and electrical conductivity in α-Gd2S3

Magnetic susceptibility and electrical resistivity of α-Gd₂S₃ with an orthorhombic structure (space group: Pnma) have been measured for powder and single-crystal samples. While the magnetic susceptibility of powder sample exhibits a broad peak having a maximum at 4.2 K, the susceptibility for a single crystal with an applied magnetic field along the b-axis demonstrates a sharp drop below 10 K. Nevertheless, the susceptibility with the field perpendicular to the b-axis keeps increasing with decreasing temperature even below 10 K. The electrical resistivity ρ for the powder sample of 4.2×10³ Ω cm around room temperature increases with decreasing temperature and shows a slight discontinuity at about 65 K. In both regions above and below 65 K, is proportional to T^−1/4 with respective coefficients, which is associated with Mott variable-range hopping conductivity. The resistivity of a single crystal along the b-axis is considerably smaller than the value for the powder sample as 0.35 Ω cm at room temperature, and its temperature dependence is fairly weak. While cooling, the resistivity first decreases down to 240 K and then keeps the value independent of the temperature down to 140 K, and subsequently rises gently below 140 K.     

Nuclear magnetic resonance on oriented109In(4.2h) and110In(4.9h) after recoil implantation into Fe

Radioactive¹⁰⁹In(j ^π=9/2⁺;T _1/2=4.2h) and¹¹⁰In(j ^π=7⁺;T _1/2=4.9h) were produced via the¹⁰⁹Ag (α, xn) reactions and recoil-implanted into Fe foils. With the technique of nuclear magnetic resonance on oriented nuclei the magnetic hyperfine splittings were investigated in external magnetic fieldsB ₀=0.5...4.2 kG. The zero-field splitting were measured as 268.9(2)MHz and 147.3(3)MHz for¹⁰⁹InFe and¹¹⁰InFe, respectively. With the known hyperfine fieldB _HF(InFe)=?286.6(5) kG the nuclearg-factors are deduced asg(¹⁰⁹In)=1.231(3) andg(¹¹⁰In)=0.674(2). Our result for¹⁰⁹In shows that theπ g _9/2 g-factors vary by only ～0.1% betweenA=109 and 115. For the |π _9/2 vd _5/2〉₇₊ of¹¹⁰In the additivity relation of magnetic moments is fulfilled to on accuracy of 0.3(3)%.