Gyromagnetic Factor Research Articles

Spin-splitting analysis of a two-dimensional electron gas in almost strain-freeIn0.89Ga0.11Sb/In0.88Al0.12Sbby magnetoresistance measurements

We investigated the spin-splitting in an almost strain-free ${\text{In}}_{0.89}{\text{Ga}}_{0.11}{\text{Sb/In}}_{0.88}{\text{Al}}_{0.12}\text{Sb}$ two-dimensional electron gas (2DEG) by magnetoresistance measurements at 1.5 K. A large effective gyromagnetic factor ($g$ factor) $|{g}^{\ensuremath{\ast}}|=33--34$ was obtained by means of the coincidence method, which assumes an effective mass ${m}^{\ensuremath{\ast}}=0.021{m}_{0}$ at the Fermi energy. In spite of the large $g$ factor and the high mobility $(\ensuremath{\mu}=9.8\ifmmode\times\else\texttimes\fi{}{10}^{4}\text{ }{\text{cm}}^{2}/\text{V}\text{ }\text{s})$, a vanishing spin-splitting was also found around $B\ensuremath{\sim}0.8\text{ }\text{T}$ by analyzing the second derivative of the magnetoresistance. This effect originates from the interplay between the Rashba and Dresselhaus spin-orbit interactions, and we theoretically confirmed the fact that the Dresselhaus spin-splitting energy $\ensuremath{\Delta}{E}_{0D}=3.5\text{ }\text{meV}$ was more than twice as large as the Rashba spin-splitting energy $\ensuremath{\Delta}{E}_{0R}=1.5\text{ }\text{meV}$. Moreover, we demonstrated that the theoretical curves of the normalized spin splitting, including the $g$ factor and the spin-orbit interactions, were well fitted to the experimental points with the Dresselhaus spin-orbit interaction. Therefore, we concluded that the Dresselhaus spin-orbit interaction is dominant in our 2DEG in spite of its narrow band gap.

Photoluminescence under magnetic field and hydrostatic pressure for probing the electronic properties of GaAsN

AbstractThe puzzling electronic properties of GaAsN have been investigated through the compositional dependence of two highly sensitive band structure parameters: the electron effective mass, me, and the electron gyromagnetic factor, ge. In the N concentration range from 0% to 0.7%, both me and ge show a highly nonlinear dependence on N composition that can be explained in terms of alternating on‐ and off‐resonance conditions between the red‐shifting conduction band edge and specific energy‐pinned N cluster states. Furthermore, the electronic properties of the material are studied under hydrostatic pressure, P. This allows tuning in a same sample the interaction between extended and localized states and disclosing a hierarchy between different nitrogen complexes as regards the extent of the perturbation these complexes exert on the electronic properties of the GaAs host crystal. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Zeeman splitting andgfactor of the1s22s22pP3∕22andP1∕22levels inAr13+

The Zeeman line components of the magnetic-dipole (M1) 1s{sup 2}2s{sup 2}2p {sup 2}P{sub 1/2}-{sup 2}P{sub 3/2} transition in boronlike Ar{sup 13+} were experimentally resolved by high-precision emission spectroscopy using the Heidelberg electron beam ion trap. We determined the gyromagnetic (g) factors of the ground and first-excited levels to be g{sub 1/2}=0.663(7) and g{sub 3/2}=1.333(2), respectively. This corresponds to a measurement of the g factor of a relativistic electron in a bound non-S state of a multielectron ion with a 1.5 parts-per-thousand accuracy. The results are compared to theoretical calculations by means of the configuration interaction Dirac-Fock-Sturmian method including electron correlation effects and additional quantum electrodynamic corrections. Our measurements show that the classical Lande g factor formula is sufficiently accurate to the present level of accuracy in few-electron ions of medium nuclear charge number Z.

Effect of antiferromagnetic exchange interactions on the Glauber dynamics of one-dimensional Ising models

We study the effect of antiferromagnetic interactions on the single spin-flip Glauber dynamics of two different one-dimensional Ising models with spin $\ifmmode\pm\else\textpm\fi{}1$. The first model is an Ising chain with antiferromagnetic exchange interaction limited to nearest neighbors and subject to an oscillating magnetic field. The system of master equations describing the time evolution of sublattice magnetizations can easily be solved within a linear field approximation and a long time limit. Resonant behavior of the magnetization as a function of temperature (stochastic resonance) is found, at low frequency, only when spins on opposite sublattices are uncompensated owing to different gyromagnetic factors (i.e., in the presence of a ferrimagnetic short range order). The second model is the axial next-nearest-neighbor Ising (ANNNI) chain, where an antiferromagnetic exchange between next-nearest neighbors is assumed to compete with a nearest-neighbor exchange interaction of either sign. The long time response of the model to a weak, oscillating magnetic field is investigated in the framework of a decoupling approximation for three-spin correlation functions, which is required to close the system of master equations. The calculation, within such an approximate theoretical scheme, of the dynamic critical exponent $z$, defined as $1∕\ensuremath{\tau}\ensuremath{\approx}{(1∕\ensuremath{\xi})}^{z}$ (where $\ensuremath{\tau}$ is the longest relaxation time and $\ensuremath{\xi}$ is the correlation length of the chain), suggests that the $T=0$ single spin-flip Glauber dynamics of the ANNNI chain is in a different universality class than that of the unfrustrated Ising chain.

The covalence effect of the gyromagnetic factor of [formula omitted

In this paper, formulas for the optical spectrum and the gyromagnetic factor for d 7 ions in T d symmetry with a slight triangle perturbation are established by using a covalent model, in which the covalence contribution has been considered. Using the model, we have calculated the optical spectra and the g -factor of CdS : Co 2 + . The calculation results agree well with the experimental findings. It suggests that covalent model should be adopted for the calculation of the optical spectrum and the EPR parameters for Co 2 + ion in covalent crystal.

Theoretical studies of the Spin Hamiltonian Parameters for the orthorhombic Pr4+ ion in SrCeO3 crystal

Abstract The perturbation formulae of the Spin Hamiltonian Parameters (EPR parameters anisotropic gyromagnetic factors g x , g y , g z and hyperfine structure constants A x , A y , A z ) for the lowest Kramers doublet of 2 F 5/2 of 4f 1 ion in orthorhombic symmetry are established. In these formulae, the contributions of the covalence effects, the admixture between J = 5/2 and J = 7/2 states as well as the second-order perturbation are all included. The crystal field parameters for the studied Pr 4+ center are calculated from the superposition model and the crystal structure data. Based on the perturbation equations and related parameters, the g factors g x , g y , g z and hyperfine structure constants A x , A y , A z for orthorhombic Pr 4+ ion in SrCeO 3 are calculated. The results are in reasonable agreement with the observed values. The results are discussed.

Sensitivity analysis framework for micromagnetism with application to the optimal shape design of magnetic random access memories

The paper concerns the Landau–Lifshitz (LL) equation with space variable gyromagnetic factor γ ⩾ 0. This allows for a flexible description of the magnetic properties of materials. The area of a domain where the material exhibits ferromagnetic behaviour is simply compact support of γ. Outside this region, material is non-magnetic (γ = 0). First, a stability analysis of the LL equation and the corresponding sensitivity equation is carried out. We have to deal with a loss of strong ellipticity due to the fact that we allow γ to vanish in a part of a domain. Therefore we introduce a regularized problem where γ > ϵ for a constant positive ϵ and we investigate the limit process ϵ → 0. Next, we apply previous theoretical results to the optimal shape design of a magnetic random access memory (MRAM) core. A primal-dual approach is employed to tackle this problem. In the last section, numerical results for the standard model of MRAM are presented.

Influence of nitrogen-cluster states on the gyromagnetic factor of electrons inGaAs1−xNx

The effective gyromagnetic factor of electrons, ${g}_{e}^{*}$, has been determined by Zeeman splitting measurements in a large number of $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}∕\mathrm{Ga}\mathrm{As}$ $(x<0.7%)$ samples. Upon $N$ incorporation, ${g}_{e}^{*}$ shows first a sign reversal with respect to that of GaAs, then increases abruptly for a nitrogen concentration of order of 0.04%, and finally displays a nonmonotonic dependence on composition for higher $x$ values. This behavior is well reproduced by a modified $\mathbf{k}\mathbf{∙}\mathbf{p}$ model taking into account a nonmonotonic loss of $\ensuremath{\Gamma}$ character of the conduction band minimum due to multiple crossings between the redshifting conduction band edge and $N$-cluster states.

Quantum information processing on spin degrees of freedom in QDs placed in diluted magnetic semiconductor

AbstractThe spin degrees of freedom in quantum dot (QD) embedded in a diluted magnetic semiconductor (DMS) medium are considered in a model of a qubit and a gate for quantum information processing (QIP). The qubit is defined as a singlet and triplet pair of states of two electrons in a He‐type QD in the DMS medium with strongly enhanced gyromagnetic factor. Methods of qubit rotation (Rabi oscillations) as well as two‐qubit operations are suggested and analyzed. Moreover, decoherence related to spin waves (magnon‐induced dephasing) in this new system (QD in DMS) is studied, and the relevant time‐scale is estimated in accordance with preliminary experimental results. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electron spin resonance and magnetization in La 0.67Ca 0.33MnO 3 thin films

We report electron spin resonance (ESR) and magnetization measurements in La 0.67Ca 0.33MnO 3 thin films deposited on LaAlO 3 single-crystal substrates by DC sputtering technique. Angular and temperature dependence of resonance field ( H Res) and ESR line-width (Δ H PP) were measured in the ferromagnetic and paramagnetic regime. Above T C, H Res is not shifted, while below T C, H Res for H ⊥ and H ∥ diverge, due to the presence of magnetic anisotropy and demagnetizing fields. Besides, when T is approaching T C from above, the Δ H PP goes to a minimum (≈200 G) and Δ H PP increases below T C. Temperature dependence of magnetization in the films was obtained by using the relationship of H Res. These values were compared with SQUID measurements. Finally, we estimated the gyromagnetic factor in 1.996(6).

Model for spin-orbit effects in two-dimensional semiconductors in magnetic fields

We analyse the interplay between Dresselhaus, Bychkov-Rashba, and Zeeman interactions in a two-dimensional semiconductor quantum system under the action of a magnetic field. When a vertical magnetic field is considered, we predict that the interplay results in an effective cyclotron frequency that depends on a spin-dependent contribution. For in-plane magnetic fields, we found that the interplay induces an anisotropic effective gyromagnetic factor that depends on the orientation of the applied field as well as on the orientation of the electron momentum.

Electron spin resonance studies on La 0.7−xDy xSr 0.3MnO 3

We have employed the technique of electron spin resonance (ESR) for studying the Dy-doping effects on the magnetic state of La 0.7− x Dy x Sr 0.3MnO 3 with x=0.35, 0.40 and 0.45. The results of temperature-dependent linewidth, gyromagnetic factor ( g-factor), double-integrated intensity (DIN) and their correlation with transport property are presented. It is found that with increasing Dy-content, the ferromagnetic phase is suppressed, driving the samples of x=0.35 and 0.40 to a spin-disorder state with a reduced magnetic transition temperature and possibly to a spin-glass state for x=0.45. Furthermore, the linewidth increases and g-factor decreases with increasing Dy-content, implying that the exchange coupling strength of Mn 3+–Mn 4+ is reduced with increasing Dy-doping.

The RKKY interaction in the presence of an external magnetic field

The Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction has been extended to the case when an external magnetic field is taken into account. It has been shown that the RKKY Hamiltonian should contain the Zeeman-like term in which the effective gyromagnetic factor occurs. This effective gyromagnetic factor contains a correction term which is linearly dependent on the contact potential between the localized spins and conduction electrons. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Projected shell model description of high spin states inCe124

The projected shell model is used to study the positive parity bands in $^{124}\mathrm{Ce}$. The energy spectra, transition quadrupole moments, and gyromagnetic factors are calculated. The calculation reproduces the observed positive parity bands. The peak in g-factors at spin $I=14$ is predicted due to proton alignment arising from the two quasiparticle (2-qp) band crossing. The wave functions of yrast states at $I=14$ to 20 are dominated by the two quasiparticle (2-qp) states. Measurement of transition quadrupole moments and g-factors would be a strong test for our predictions.

Theoretical Studies on the Gyromagnetic Factors and the Hyperfine Structure Constants for the Tetragonal Copper Center in KTaO3

The gyromagnetic factors g∥, g⊥ and the hyperfine structure constants A∥ and A⊥ of the tetragonal Cu2+ center in KTaO3 are theoretically studied in this work. Based on the analyses of the electron paramagnetic resonance results of this center, it is found that the impurity Cu2+ occupies the octahedral Ta5+ site, associated with a nearest-neighbouring oxygen vacancy VO along the C4 axis. Due to the electrostatic repulsion of VO, Cu2+ is displaced away from VO by ΔZ(≈ −0.29 Å ) along the C4 axis. The theoretical values of the g and A factors based on the above defect structure and the impurity displacement agreee reasonably with the experimental data.

Noncommuting Coordinates, Exotic Particles, and Anomalous Anyons in the Hall Effect

Our previous ``exotic'' particle, together with the more recent anomalous anyon model (which has arbitrary gyromagnetic factor $g$) are reviewed. The non-relativistic limit of the anyon generalizes the exotic particle which has $g=0$ to any $g$.When put into planar electric and magnetic fields, the Hall effect becomes mandatory for all $g\neq2$, when the field takes some critical value.

Broadening of ferromagnetic resonance linewidth in [formula omitted

We studied electron spin resonance (ESR) in an ordered double perovskite Ba 2 FeMoO 6 with the Curie temperature T C = 340 K . The T-independent gyromagnetic factor at T > T C is estimated as g ∼ 2 , suggesting that Fe 3 + is probed in the paramagnetic resonance. Below T C , the resonance signal shifts to lower fields with broadening of the linewidth. The linewidth increases down to our lowest temperature. Using the two-magnon scattering relaxation mechanism quantitatively reproduces the temperature dependence of the linewidth.

Two-neutrino positron double-beta decay of 106Cd for the 0+ → 0+ transition

The two neutrino positron double beta decay of $^{106}$Cd for 0$^{+} \to $ 0$^{+}$ transition has been studied in the Hartree-Fock-Bogoliubov model in conjunction with the summation method. In the first step, the reliability of the intrinsic wave functions of $^{106}$Cd and $^{106}$Pd nuclei has been tested by comparing the theoretically calculated results for yrast spectra, reduced $B(E2$:$0^{+}\to 2^{+})$ transition probabilities, quadrupole moments $Q(2^{+})$ and gyromagnetic factors $g(2^{+})$ with the available experimental data. In the second step, the nuclear transition matrix element $M_{2\nu}$ and the half-life $T_{1/2}^{2\nu}$ for 0$^{+}\to$ 0$^{+}$ transition have been calculated with these wave functions. Moreover, we have studied the effect of deformation on nuclear transition matrix element M$_{2\nu}.$

Theoretical Studies On The Gyromagnetic Factors For Nd3+ In Scheelites-Type ABO4 Compounds

The gyromagnetic factors for Nd3+ in scheelite-type ABO4 compounds (A = Cd, Ca, Pb, Ba; B = Mo, W) are theoretically studied by the perturbation formulas of the anisotropic g factors g∥ and g⊥ for a 4f3 ion in tetragonal symmetry. In these formulas, the contributions to the g factors due to the second-order perturbation terms and the admixtures of various energy levels are taken into account. The relevant crystal-field parameters are determined by the superposition model and the local geometrical relationship of the A2+ sites occupied by the impurity Nd3+. The obtained g factors agree reasonably with the observed values. The discrepancies between theory and experiment are discussed.

Avoiding superluminal propagation of higher spin waves via projectors onto W2 invariant subspaces

We propose to describe higher spins as invariant subspaces of the Casimir operators of the Poincaré Group, P2, and the squared Pauli–Lubanski operator, W2, in a properly chosen representation, ψ(p) (in momentum space), of the Homogeneous Lorentz Group. The resulting equation of motion for any field with s≠0 is then just a specific combination of the respective covariant projectors. We couple minimally electromagnetism to this equation and show that the corresponding wave fronts of the classical solutions propagate causally. Furthermore, for (s,0)⊕(0,s) representations, the formalism predicts the correct gyromagnetic factor, gs=1/s. The advocated method allows us to describe any higher spin without auxiliary conditions and by one covariant matrix equation alone. This master equation is only quadratic in the momenta and its dimensionality is that of ψ(p). We prove that the suggested master equation avoids the Velo–Zwanziger problem of superluminal propagation of higher spin waves and points toward a consistent description of higher spin quantum fields.