Magnetic moment of phonons in graphene induced by a magnetic field

A magnetic field not only changes the electronic structure in graphene but also affects the phonon excitations via the electron-phonon interaction and even enables the phonons to generate magnetism. In this paper, we evaluate the magnetic moment of phonons in graphene using a generating-functional technique. The calculation results indicate that the phonon magnetic moment exists only in a weak magnetic field. The step-like change of the magnetic moment with the magnetic field reflects a macroscopic quantum effect.     

Neutrino induced magnetic moment and spin precession

When propagating through a dispersing medium, a massive neutrino acquires an induced magnetic moment that may give rise to a helicity flip in an external magnetic field with a larger probability than that caused by the anomalous magnetic moment. This phenomenon is investigated in the framework of relativistic quantum mechanics and of the generalized Bargmann–Michel–Telegdi equation.     

On the induced cobalt moment in RCo4 B-type compounds

The results of magnetic measurements performed on (Gd_xY_1-x)Co₄B compounds in the temperature range 4.2 and 900 K are reported. The compounds with x ⩾ 0.2 are ferrimagnetically ordered. The mean cobalt moment is dependent on composition. Above the Curie temperatures, the reciprocal susceptibilities obey a non-linear dependence as function on temperature. By using a two sublattices model, the mean values of the molecular field coefficients, characterizing the magnetic interactions inside and between sublattices are determined. The mean cobalt moments are linearly dependent on the exchange fields acting on these atoms.     

The electron magnetic moment at high temperature

The one-loop QED correction to the electron magnetic moment is computed at high temperature. We find that the correction reduces the magnetic moment.     

The evolution of the magnetic moment in a corrugated magnetic field

In the first part, the equations of motion in a weakly corrugated, periodic magnetic field are linearized and solved by using paraxial approximation, to describe the model and the associated resonance condition. In the second part, the nonlinear evolution of the magnetic moment of resonant particles, in connection with their axial displacement is investigated analytically by using the multiple scale method. It is seen that the linear evolution is converted into a slow and periodic oscillation around the unperturbed value, with a considerable amplitude. The analytic expressions for the period and amplitude of the oscillations are derived and compared with the numerical simulations, which are also presented. Finally, the limitations of the paraxial approximation are concluded by investigating the numerical simulations, with actual field expressions. (c) 1997 American Institute of Physics.     

Magnetic field driven domain-wall propagation in magnetic nanowires

The mechanism of magnetic field induced magnetic domain-wall (DW) propagation in a nanowire is revealed: A static DW cannot exist in a homogeneous magnetic nanowire when an external magnetic field is applied. Thus, a DW must vary with time under a static magnetic field. A moving DW must dissipate energy due to the Gilbert damping. As a result, the wire has to release its Zeeman energy through the DW propagation along the field direction. The DW propagation speed is proportional to the energy dissipation rate that is determined by the DW structure. The negative differential mobility in the intermediate field is due to the transition from high energy dissipation at low field to low energy dissipation at high field. For the field larger than the so-called Walker breakdown field, DW plane precesses around the wire, leading to the propagation speed oscillation.     

Nuclear magnetic moment: Relativistic mean field description

Valence nucleon effective mass, which is almost constant, is proposed within the relativistic mean field theories of finite nuclei (closed shell ± one nucleon). It acquires a slight spin-orbit splitting due to relativistic effects. The relativistic Dirac magnetic moment is rewritten analytically in terms of angular momentum-Pauli spin coupled states and the effective mass. Introducing the nucleon effective charge, the iso-scalar and iso-vector corrections to the magnetic moment operator are extracted from the overall one parameter fit of the measured and the calculated values. The calculated values of magnetic moments are in overall fair agreement with the experiment as well as with the other detailed microscopic calculations.     

Vacuum magnetic moment of an electron moving in a uniform magnetic field

The methods of quantum electrodynamics are used to study the dependence of the vacuum magnetic moment of the electron on its energy and on the magnetic field intensity. This dependence is most important in the case of strong magnetic fields. For an ultrarelativistic electron, the vacuum magnetic moment turns out to depend on the electron energy, even in a weak magnetic field.Translated from Izvestiya VUZ. Fizika, Vol. 11, No. 11, pp. 17–22, November, 1968.     

Diameter-dependent coercivity of cobalt nanowires

We show that the coercivity of electrochemically grown cobalt nanowires (NWs) within the pores of a polycarbonate membrane can be changed to a large extent by tuning their diameters. The face centered cubic crystalline structure of the NWs having diameter in the range of 10 to 200 nm could be retained. Smaller diameter wires (below 30 nm) are found to be single crystalline and oriented in the [110] growth direction, but for higher diameter wires the crystallite size became very small. Magnetization measurements with an applied field parallel to the axis of the NWs show that the nature of the M–H loop changes from square to linear as the diameter of the NWs increases. The coercivity was found to be 1700 Oe and 480 Oe at 5 K (1000 Oe and 250 Oe at 300 K) for 10 nm and 100 nm wires, respectively. The observed changes in the nature of the M–H loop and in coercivity could be explained following the Stoner–Wohlfarth model and using the fact that the domain size reduces as the diameter of the wires increases.     

States of cobalt fluoride in a strong magnetic field

The behavior of the magnetic subsystem of cobalt fluoride is investigated in a strong magnetic field oriented in an arbitrary direction in space. In the case where the magnetic field is out of the planes passing through the easiest magnetization axis A and the axis [100] ‖ X or through the easiest magnetization axis A and the axis [010] ‖ Y, it follows from the derived system of equations that the antiferromagnetic vector l does not change direction to be align with the basal plane, provided the magnetic field has a nonzero component along the A axis. It is demonstrated that the antiferromagnetic vector l becomes parallel to the basal plane only when the magnetic field is perpendicular to the A axis. The case of the magnetic field directed parallel to the [110] axis is examined thoroughly. The critical value of the magnetic field is determined at which the antiferromagnetic vector l becomes parallel to the basal plane and perpendicular to the external magnetic field H for H _⊥ → ∞.     

Structural and magnetic properties of high magnetic moment electroplated CoNiFe thin films

CoNiFe alloy thin films deposited at various cobalt concentrations were galvanostatically electrodeposited on the pre-cleaned copper substrates. The effects of cobalt concentration on the structural, compositional, morphological, and magnetic properties of the films were investigated. X-ray diffraction patterns revealed that the deposited films possess polycrystalline in nature with mixed (fcc–bcc) cubic structure at optimized cobalt concentration. Microstructural properties of the films were calculated from predominant diffraction lines. The surface morphology and surface roughness were characterized using scanning electron microscopy and atomic force microscopy, respectively. EDAX results were revealed that the cobalt content increases as nickel content decreases whereas ferrous content initially increases and then eventually decreases in the CoNiFe alloy. VSM results show a higher value of saturation magnetization (4πM _s) above 2 T with coercivity 154 A/m for films deposited in the optimized deposition condition.     

Magnetic moment of relativistic quark gas in intense magnetic field

Magnetic properties of a system of noninteracting relativistic quark gas in presence of an external intense magnetic field has been calculated assuming that quarks obey parastatistics of order three. It is found, although the magnetization is greater for quark gas than that for normal hadronic system, it is unlikely that the spontaneous magnetization will take place in a quark star.     

Anomalous temperature dependence of the magnetic field induced antiferromagnetic moment in the antiferroquadrupolar ordered state of CeB6

The magnetic field induced antiferromagnetic moment M(AF) at low magnetic fields in the antiferroquadrupolar (AFQ) ordered phase of CeB6 was investigated by elastic neutron diffraction experiments for H parallel [110]. The peak intensity at the AF magnetic reciprocal point (1 / 2,1 / 2,1 / 2) corresponding to M(2)(AF) increases with decreasing temperature below the AFQ ordering temperature T(Q), and exhibits a broad maximum at T approximately 3 K and decreases with a further decrease of temperature. This unusual behavior of M(AF) at low fields is explained as a result of the competition between the AF-octupolar and AF-exchange interactions in the O(xy) type AFQ ordered state.     

Dielectrophoretic assembly of ZnO nanowires

The synthesis of zinc oxide （ZnO） nanowires is achieved by vapor phase transportation （VPT） method. The designed quartz tube, whose both ends are narrow and the middle is wider, is used to control the growth of ZnO nanowires. Dielectrophoresis （DEP） method is employed to align and manipulate ZnO nanowires which are ultrasonic dispersed and suspended in ethanol solution. Under the dielectrophoretic force, the nanowires are trapped on the pre-patterned electrodes, and further aligned along the electric field and bridge the electrode gap. The dependence of the alignment yield on the applied voltage and frequency is investigated.     

Field induced magnetic moment and anisotropy of HoAG and TbAG

A theoretical and experimental study of the field induced magnetic moment and magnetic anisotropy of holmium aluminum garnet and terbium aluminium garnet is presented. The torque curves due to the induced field dependent anisotropy obtained at 4.2 K in applied fields up to 7 T are compared with the theoretical calculation. The results indicate that the two systems show remarkably similar magnetic behaviours, and the calculation based upon a simplified effective Hamiltonian with the crystal field parameters determined from spectroscopic data accounts for the experimental results with satisfactory accuracy.     

Interface profile evolution between binary immiscible fluids induced by high magnetic field gradients

A mechanical analysis is done to find the evolution of the interface profile between binary immiscible fluids induced by a three-dimensional orthogonal magnetic field gradient.In the experiments,the changes of the interface profile between four groups of binary immiscible fluids are investigated under the same horizontal magnetic field gradients.The binary immiscible fluids are made of benzene and other liquids,like CuSO4,Fecl3,FeSO4 or Cucl2 aqueous solutions.In addition,the interface profile between the benzene and CuSO4 aqueous solution is examined under different horizontal magnetic field gradients.The experimental results are consistent with the theoretical analysis.This study explains the enhanced Moses effect from a mechanics standpoint.Furthermore,a new method for susceptibility measurement is proposed based on this enhanced Moses effect.