Ordering of Ground State Energy Levels of Two-Electron Quantum Dot in a Magnetic Field

The energy levels structure of two interacting electrons in a parabolic quantum dot under an external magnetic field of arbitrary strength is studied via the asymptotic iteration method. The method gives accurate results over the full range of quantum dot parameters. A crossings between spin-singlet and spin-triplet ground states energies as a function of the magnetic field is predicted.     

Magnetic Quantum Tunnelling in Faster Relaxation Process in Mn12Ac Molecular Magnets

The field-tuned ac susceptibility of Mn12Ac single crystal has been measured as functions of temperature and frequency. Two relaxation processes appear in our measurement. One is related to the magnetic quantum tunnelling of a collective spin S = 12 by a 61 K magnetic barrier and it has been well studied, while the other is faster than the former and its mechanism is unclear. We find that the relaxation time for the faster process shows the minima at H = 0 and H = 3.4 kOe, indicating that the quantum tunnelling also takes place in this process while the resonant fields are different from what we have known before.     

Ground State Phases of Spin-Orbit Coupled Spin-1 Dipolar Bose-Einstein Condensates

International Journal of Theoretical Physics - The ground state phases of spin-1 Bose-Einstein condensates with Rashba spin-orbit coupled (SOC) and dipole-dipole interaction (DDI) are studied....     

Spin-Wave Resonance in Ge : Mn Thin Films with Percolation Magnetic Ordering

The mechanism of excitation and propagation of spin waves in Ge: Mn thin films with different nominal manganese concentrations (2, 4, and 8 at % Mn) with percolation magnetic ordering is explored. Concentration dependencies of Curie temperature T_C(n) and spin wave rigidity D(n) are determined, which enables to find the index of correlation distance. An exotic percolation magnetic state of samples of Ge: Mn thin films is confirmed by rectifying experimental dependences D(n) and D/T_C(n) in coordinates accepted in the percolation theory.     

Magnetic Properties of Dipolar Chains in Ferrofluids

We have investigated the dipole interaction energies per particle and the local dipole field distributions in a frozen-magnetization model of a ferrofluid chain in a saturating magnetic field. A lognormal distribution of particle diameters was assumed. The interaction energies were calculated for one-dimensional arrays of dipoles with moments parallel to the chain. We have computed the energies by various approximations related to the hard sphere particle diameter distribution. A similar approach was followed for the local field distributions. It was found that the energy per particle and mean local field were largely determined by the mean particle diameter, but the distribution of local fields was sensitive to both the mean diameter and the assumptions about spatial correlations between particles of different size. Detailed results are presented for water-soluble Fe₃O₄/PAA (polyacrylic acid).     

Ground State of a Two-Sublattice Anisotropic Ferromagnet in a Magnetic Field

Physics of the Solid State - The ground state of a classical two-sublattice ferromagnet with the noncollinear single-ion anisotropy axes of the sublattices and the antisymmetric and anisotropic...     

Ground State Energy of Large Atoms in a Self-Generated Magnetic Field

We consider a large atom with nuclear charge Z described by non-relativistic quantum mechanics with classical or quantized electromagnetic field. We prove that the absolute ground state energy, allowing for minimizing over all possible self-generated electromagnetic fields, is given by the non-magnetic Thomas-Fermi theory to leading order in the simultaneous Z → ∞, α → 0 limit if Z α ² ≤ κ for some universal κ, where α is the fine structure constant.     

Charge-orbital Ordering,Magnetic State,and Exchange Couplings in Quasi-One-Dimensional Vanadate V6O13

JETP Letters - Charge and orbital ordering, magnetic state, and exchange couplings in quasi-one-dimensional vanadate V6O13, a potential cathode material for Li-ion batteries, are investigated using...     

磁场中多原子极性晶体中体极化子的基态能量

研究磁场中多原子极性晶体中体极化子的性质,采用线性组合算符法,分别导出强,弱耦合情形下体极化子的基态能量。     

Dipolar Order in Molecular Fluids: II. Molecular Influence

The influence on the short-range packing in dipolar fluids by molecular shape and by additional higher order electrostatic moments has been investigated by molecular dynamic simulations. The dipole polarization was found to decrease as the particles were elongated parallel to the dipole and to increase for elongation perpendicular to the dipole, eventually forming a nematic order. The addition of a quadrupole lead to a reduction of the polarization, and the influence of an axial octupole was weaker and more complex. Both a decrease and an increase of the polarization is possible depending on the relative dipole–dipole and octupole–octupole interaction strengths and the relative direction of the symmetry axes of the moments. These observations were attributed to the different parity of a dipole and a quadrupole and the same parity of a dipole and an axial octupole under reflection. In addition, further insights into the formation of dipole polarization were obtained. Short polar and long equatorial radii and strong dipole–dipole interaction are particle properties that promote a fluid with a high dipole polarization.     

Orientation Information from the Dipolar Interaction Between a Complex in the Excited Quartet State and a Doublet Spin Label

An algorithm is proposed for deriving the position of a stable radical relative to a photoexcited quartet state from the electron spin–spin interactions measured by double resonance methods. Intersystem crossing generates multiplet polarization in the quartet state and microwave excitation of the ±3/2 ? ±1/2 transitions converts the multiplet polarization into net polarization of the ±1/2 levels. The dependence of the electron spin echo envelope modulation (ESEEM) of the +1/2 ? ?1/2 transition on the field/frequency of the stimulation pulse is demonstrated. The algorithm is tested by comparing the predicted ESEEM patterns to those from explicit numerical calculations of the spin evolution (so-called numerical experiments), which act as a model for experiment results. The comparison demonstrates that within the point-dipole approximation it is feasible to obtain not only the distance between the two paramagnetic centers but also the orientation of the distance vector relative to the principal axes of the quartet state.     

类钙钛矿化合物Ca(Mn2 Cu1)Mn4 O12的磁性与磁电阻效应

利用固相反应法制备了名义成分为Ca(Mn2 Cu1 )Mn4 O1 2 的类钙钛矿锰氧化物 .x射线衍射表明 ,为了获得较为致密的样品和减小杂相含量 ,可以采用高温烧结再在 10 73K长时间空气中退火的制备方法 .样品在低温下同时存在铁磁相和反铁磁相 ,由于反铁磁相的存在导致样品在 4 5K时的磁化强度显著降低 ,并在 8T的高磁场下仍未达到饱和 .样品呈半导体导电性质 ,在 85K和 6T磁场下磁电阻比的最大值可达 - 4 6 % .     

Frustrations and Ordering in Magnetic Systems of Various Dimensions

Based on the exact and numerical calculations within the Ising and Potts models on lattices of various types and dimensions (one-dimensional, square, triangular, hexagonal, kagome, simple cubic, and body-centered cubic), magnetic orderings, phase transitions, and frustrations were investigated, taking into account the exchange interactions between magnetic moments at the nearest and next-nearest nodes and an external magnetic field. The causes of the occurrence of frustrations are found, and the essential features of the behavior of frustrated systems that distinguish them from the nonfrustrated systems are determined.     

Magnetic after-effect in Mn ferrite

The ballistic method was used to study the disaccommodation of magnetic inductionB in Mn_1.36Fe_1.64O₄ in a d.c. magnetic fieldH 0·040–5·5 Oe. The experimental results were interpreted from the point of view of the irreversible displacements of walls. It was shown that under certain assumptions it is possible to derive the statistical distribution of Bloch wall energies from the experimental curves for substances in which there exists magnetic diffusion aftereffect.     

Equation of State of the Strong Interaction Matter in an External Magnetic Field

We investigate the equation of state of the strong interaction matter in a background magnetic field via the two flavor Nambu–Jona-Lasinio model. Starting from the mean-field thermodynamical potential density ?, we calculate the pressure density p, the entropy density s, the energy density ε, and the interaction measure(ε- 3p)/T4 of the strong interaction matter at finite temperature and finite magnetic field. The results manifest that the chiral phase transition is just a crossover but not a low order phase transition. Moreover there may exist magnetic catalysis effect, and its mechanism is just the effective dimension reduction induced by the magnetic field.     

Magnetic Moment of the 3/2− Ground State of 185W

Nuclear magnetic resonance measurement have been performed for ¹⁸⁵W oriented at 8 mK in an Fe host. The magnetic hyperfine splitting frequency at an external magnetic field of 0.1 T was determined to be 196.6(2) MHz. With the known hyperfine field of B _hf = −71.4(18) T, the nuclear magnetic moment of ¹⁸⁵W is deduced as μ(¹⁸⁵W) = +0.543(14) μ_N.