Dependence of electron spin g-factor on magnetic field in quantum wells

The dependence of electron spin g-factor on magnetic field has been investigated in GaAs/AlGaAs quantum wells. We have estimated the electron g-factor from spin precession frequency in time-resolved photoluminescence measurements under a magnetic field in different configurations; the magnetic field perpendicular (g_⊥) and parallel (g_∥) to the quantum confinement direction. When the angle between the magnetic field and the confinement direction is 45°, we have found that g-factor varies depending on the direction of magnetic field and the circular polarization type of excitation light (σ⁺ or σ^?). These dependences of g-factor exhibit main features of Overhauser effect that nuclear spins react back on electron spin precession. The value of g_⊥ and g_∥ corrected for the nuclear effects agree well with the results of four-band k·p perturbation calculations.     

Two-loop diagrams in Yang-Mills theory

A calculation of the renormalisation constants of the Yang-Mills field to O(g⁴) is presented. The function β(g) is hence evaluated to O(g⁵) and possible implications for gauge theories of the strong interactions discussed.     

Unified calculations of the optical and electron paramagnetic resonance spectral data for Ce ion in Y3Ga5O12 crystal

Seven crystal field energy levels (obtained from the optical spectra) and three g factors g_x, g_y and g_z (obtained from electron paramagnetic resonance (EPR) spectra) for Ce³⁺ ion in Y₃Ga₅O₁₂ crystal are calculated together by diagonalizing a complete energy matrix. The Hamiltonian of this energy matrix includes all the interactions for 4f¹ ion Ce³⁺ in rhombic crystal field and under an external magnetic field, and so the optical and EPR data can be studied in a unified way. The calculated crystal field energy levels are in better agreement with the experimental values than the calculated values in the previous paper, and the g factors (which have not been calculated previously) are explained reasonably. The results are discussed.     

Transient field measurements of g-factors for 24Mg AND 26Mg

The g-factors of the first-excited J^π = 2⁺ states of ²⁴Mg and ²⁶Mg have been measured with the ion-implantation perturbed angular correlation technique (IMPAC). The precession of the spins of nuclei recoiling into a magnetized iron backing is predominantly caused by the transient magnetic field for these very light and short-lived (τ_m ≈ 1 ps) nuclei. The transient field, which attains a value of 200 T for the Mg isotopes, is present only during the slowing-down of the recoiling nucleus and results in average precession angles of about 1.5 mrad. The experimental results are treated in the framework of the transient field theory of Lindhard and Winther. This yields g-factors of g = +0.42b ± 0.09 and g = +1.3 ± 0.3 for ²⁴Mg and ²⁶Mg, respectively. The results are compared with theoretical predictions and for ²⁴Mg also with a recent time-differential deorientation experiment.     

Far-infrared absorption of MgO: Fe2+ in magnetic fields

We have measured the far-infrared absorption of iron-doped MgO in the wavenumber region 10–200 cm^?1 and in magnetic fields up to 6 T. Absorption peaks found at 107.0 and 110.5 cm^?1 are assigned to magnetic dipole transitions between the spin-orbit Г_5g groundstate (J = 1) and the Г_3g, Г_4g excited states (J = 2) of the Fe²⁺ -ion at a cubic site. The observed magnetic field dependence shows that Г_4g is the higher excited level, so that the crystal field order of the levels is not changed by the reduction of the spin-orbit splitting attributed to a dynamic Jahn-Teller effect. An additional absorption peak at 33.4 cm^?1 is found to split in magnetic field.In iron-doped KMgF₃ absorption peaks at 52 and 87 cm^?1 that have previously been attributed to the same transitions of Fe²⁺ are found to remain unshifted and unsplit in magnetic fields up to 6 T.     

Studies of the crystal field energy levels and g factors for Ce in LiYF4 crystal

The five observed crystal field energy levels and EPR g factors g_//and g_⊥ for Ce³⁺-doped LiYF₄ crystal are calculated together from a complete diagonalization (of energy matrix) method. In the method, the contributions to g factors of ground Kramers doublet from all the rest doublets within the ground and excited manifolds ²F_5/2 and ²F_7/2 are included. The calculated results show reasonable agreement with the experimental values. The calculations suggest that the crystal field parameter B₂₀ > 0 in LiYF₄: Ce³⁺ crystal. The opinion of the parameter B₂₀ < 0 in the previous paper is not correct. Since this opinion is based on the calculation of g factors using a very simple method where only the contributions to g factors from the doublets within the ground manifold ²F_5/2 are considered, it is suggested that this simple method is not effective in the calculation of g factors for 4f¹ ions in crystals.     

Theg-factor of the first 2+ state in192Pt by measurement of recoil into vacuum

Perturbed γ-ray angular distributions from the first 2⁺ states were measured for Coulomb-excited^{192,194,196,198}Pt recoiling into vacuum atv/c=0.010. Comparableg-factors were obtained for all four nuclei. Normalisation to the hyperfine field in¹⁹⁶Pt enabled both a comparison with a recent hydrodynamicg-factor measured in¹⁹²Pt and a cross-check of disputed Ir in Fe measurements. The followingg-factor was obtained:g(316 keV, 2⁺;¹⁹²Pt)=0.32(3).     

Spin-Hamiltonian theory of orbital near-degenerate state in tetragonal field

In this paper, a Spin-Hamiltonian theory of orbital near-degenerate state in tetragonal field is presented. For orbital doublet ²E, which is an orbital degenerate state in the cubic field and is a near-degenerate state in the tetragonal field, we obtain the cubic invariant form and the tetragonal invariant form of the Spin-Hamiltonian. In case of near-degeneracy (tetragonal splitting is very small) two additional g-factors are introduced to investigate Zeeman-splitting for tetragonal field. The two additional g-factors g_2z and g_2xy describe the magnetic interest between A_1g and B_1g states for a parallel magnetic field with z-axis and a perpendicular magnetic field with z-axis, respectively. The theory is based on the time-reversal invariant and the point-group symmetry invariant. The theoretical method can also be used for other orbital degenerate states ^2S+1Γ including and Γ=T₁ or T₂ and can be used for other point-group symmetry.     

Effects of effective potential on g-factor in Si inversion layers

Taking into consideration the effective potential and the magnetic field dependent dielectric function, the effective g-factor and the magnetic susceptibility have been calculated. Results show that both quantities oscillate with magnetic field.The amplitude of the effective g-factor found in this way has the value between 3.26 and 2.49 for surface electron densities n ranging from 1.0×10¹² to 7.0×10¹² cm^-2. The enhancement of g-factor is divided into two parts, noninteracting and interacting part. The interacting part is dominant and shows $\text{n}{}^{\mathrm{<mtext>-3</mtext><mtext>2</mtext>}}$ behavior.     

Frequency modulation of the 6.2 keV Mössbauer states of181Ta

Mössbauer sidebands up to the first order from a single parent line have been produced by subjecting a non magnetic W(¹⁸¹W) Mössbauer source to a strong oscillating magnetic field of up to 230 Oe amplitude and a frequency of about one megahertz. The sidebands positions and intensities agree very well with theory, which is based on a periodic time-dependent interaction of the magnetic field with the nuclear magnetic moments of ground and excited states, respectively. From the sideband intensity ag-factor ratio ofg _e /g _g =1.75(6) was derived.     

Anomalies in the orbital magnetism of neutrons in the 190,192Pt nuclei

For the ^190,192Pt nuclei, the g factors of the ν9/2^?[505]?ν11/2⁺[615] 10^? isomeric states populated in the relevant (α, 2n) reactions are measured by the method of an integrated disturbed angular distribution in an external magnetic field. From these measurements, it follows that the g factors are 0.009(8) and 0.010(6) for ¹⁹⁰Pt and ¹⁹²Pt, respectively. From the above g factors, it is found that the anomalous g _l factor of the neutron is δg _l(n)=?0.017(6).     

Absorption spectrum of VO2+ in zinc cesium sulphate hexahydrate

Results of optical absorption spectra of VO²⁺ ion doped in zinc cesium sulphate hexahydrate are reported. The observed bands have been assigned transitions from the ground ²B_2g state to the excited ²E_g, ²B_ig and ²A_1g states. From the nature and position of the bands a successful interpretation of all observed bands could be made. The crystal field and molecular orbital coefficients are reported.     

Spin precession of Po in Ni detected by In-beam conversion electrons and the magnetic moment of the 15− isomer in204Po

The magnetic moment of the 11 ns, 15^? isomer in²⁰⁴Po and the internal magnetic field of Po in Ni were determined in an in-beam recoil implantation experiment. Time-differential perturbed angular distributions of conversion electrons were measured in an iron-free orange spectrometer. The magnetic hyperfine field of ¦H(PoNi)¦=555(22) kOe is in agreement with the systematic trend for the 6p elements. Theg-factorg(15^?) =0.41(2) is discussed, together with theB (E2, 15^?→13^?). within the shell model.     

Nuclearg factors of the first and second 2+ states in192,194Pt

Theg factors of the first and second excited 2⁺ states in¹⁹²Pt and¹⁹⁴Pt have been measured using γ-γ angular correlations perturbed by the hyperfine field in an iron lattice. Bulk magnetizations of sources were examined with special care for different shapes of alloys and different magnetizing conditions. The following results have been obtained:¹⁹²Pt: 316 keV stateg=0.346±0.024, 612 keV stateg=0.455±0.089.¹⁹⁴Pt: 328 keV stateg=0.354±0.031, 622 keV stateg=0.316±0.029. These values are the largest ones which have been reported so far. The discrepancies between the present and previous data are discussed especially in terms of magnetizing conditions for the sources used. It is suggested that the difference ing factor between the first and second 2⁺ states may be in a certain correlation with M1 matrix element connecting these two states.     

Vector boson in the constant electromagnetic field

The propagator and the complete sets of in-and out-solutions of the wave equation, together with the Bogoliubov coefficients relating these solutions are obtained for the vector W-boson (with the gyromagnetic ratio g=2) in a constant electromagnetic field. When only the electric field is present, the Bogoliubov coefficients are independent of the boson polarization and are the same as for the scalar boson. For the collinear electric and magnetic fields, the Bogoliubov coefficients for states with the boson spin perpendicular to the field are again the same as in the scalar case. For the W ^? spin parallel (antiparallel) to the magnetic field, the Bogoliubov coefficients and the one-loop contributions to the imaginary part of the Lagrange function are obtained from the corresponding expressions for the scalar case by the substitution m ² → m ²+2eH (m ² → m ²-2eH). For the gyromagnetic ratio g=2, the vector boson interaction with the constant electromagnetic field is described by the functions that can be expected by comparing the scalar and Dirac particle wave functions in the constant electromagnetic field.     

EPR and optical absorption studies of Cr ions in potassium sodium dl-tartrate tetrahydrate

EPR spectra of Cr³⁺ ions doped in potassium sodium dl-tartrate tetrahydrate single crystals are recorded at 77 K. The spin Hamiltonian and zero field parameters g, |D| and |E| are measured from the resonance lines obtained at various rotations of the magnetic field. The values obtained are: g_x=1.9257±0.0002, g_y=1.9720±0.0002, g_z=2.0102±0.0002, |D|=313±2 (×10⁻⁴) cm⁻¹ and |E|=101±2 (×10⁻⁴) cm⁻¹. From the results of EPR study, the site symmetry of Cr³⁺ ion in the crystal is discussed. The optical absorption at room temperature is also studied. From the observed band positions, the crystal field splitting parameter (D_q) and the Racah inter-electronic repulsion parameters (B and C) are evaluated. The bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed.     

Determination of the g-factor of electrons in N-type silicon surface inversion layers

The g-factor of conduction electrons in the surface inversion layer on a silicon (100) surface has been determined using the tilted magnetic field method developed by Fang and Stiles.The value of (m¹/m₀)·g at the fixed magnetic field was independent of surface carrier density n_s, whereas it had a sharp peak at about 97 koe. At strong magnetic field limit the value was constant and 0.4. If we take the effective mass of conduction electrons in the inversion layer on the (100) surface as 0.2m₀, the g-factor is about two which is the same as that for conduction electrons in bulk silicon.     

Magnetic moment of the 1,307 keV state in69As

The Larmor precession of the 1,307 keV 2 ns state in⁶⁹As in an external magnetic field of 2 T has been observed in a time integral perturbed angular distribution experiment. The deducedg-factor ofg=1.05±0.13 confirms the rather pureg _9/2 proton structure of this state on which a triaxial rotational aligned band is built.     

Crystal field splitting of gadolinium in single crystals of metallic LaBi

Resolved fine structure has been observed in the ESR of Gd³⁺ in metallic LaBi single crystals. The parameter b₄=+63.7 Oe characterizes a very large cubic crystal field splitting. The g factor of g=2.002 is interpreted as evidence of s-f exchange interaction.