Modelling Magnetoresistance Effect in Limited Anisotropic Semiconductors

A macroscopic model of the magnetoresistance effect in limited anisotropic semiconductors is built. This model allows us to solve the problem of measurement of physical magnetoresistance components of crystals and films.Based on a unified mathematical model the method is worked out enabling us to measure tensor components of the specific electrical resistance and the relative magnetoresistance of anisotropic semiconductors simultaneously.     

Gate-Voltage-Induced Magnetization Reversal and Tunneling Anisotropic Magnetoresistance in a Single Molecular Magnet with Temperature Gradient

We study the control of gate voltage over the magnetization of a single-molecule magnet(SMM) weakly coupled to a ferromagnetic and a normal metal electrode in the presence of the temperature gradient between two electrodes.It is demonstrated that the SMM's magnetization can change periodically with periodic gate voltage due to the driving of the temperature gradient.Under an appropriate matching of the electrode polarization,the temperature difference and the pulse width of gate voltage,the SMM's magnetization can be completely reversed in a period of gate voltage.The corresponding flipping time can be controlled by the system parameters.In addition,we also investigate the tunneling anisotropic magnetoresistance(TAMR) of the device in the steady state when the ferromagnetic electrode is noncollinear with the easy axis of the SMM,and show the jump characteristic of the TAMR.     

Anomalous Magneto-Transport Behavior in Transition Metal Pentatelluride HfTe_5

There is a long-standing confusion concerning the physical origin of the anomalous resistivity peak in transition metal pentatelluride HfTe_5.Several mechanisms,such as the formation of charge density wave or polaron,have been proposed,but so far no conclusive evidence has been presented.In this work,we investigate the unusual temperature dependence of magneto-transport properties in HfTe_5.It is found that a three-dimensional topological Dirac semimetal state emerges only at around T_p(at which the resistivity shows a pronounced peak),as manifested by a large negative magnetoresistance.This accidental Dirac semimetal state mediates the topological quantum phase transition between the two distinct weak and strong topological insulator phases in HfTe_5.Our work not only provides the first evidence of a temperature-induced critical topological phase transition in HfTe_5 but also gives a reasonable explanation on the long-lasting question.     

Impurity States in Semimagnetic Quantum Well Wire with Anisotropic Confinement along In-Plane Directions

Journal of Experimental and Theoretical Physics - The effect of shape of the confining potential along two different confined directions in Quantum Well Wire (QWW) on the heavy hole binding energy...     

A Theory for Anisotropic Magnetoresistance in Materials with Two Vector Order Parameters

Anisotropic magnetoresistance(AMR) and related planar Hall resistance(PHR) are ubiquitous phenomena of magnetic materials. Although the universal angular dependences of AMR and PHR in magnetic polycrystalline materials with one order parameter are well known, no similar universal relation for other class of magnetic materials are known to date. Here a general theory of galvanomagnetic effects in magnetic materials is presented with two vector order parameters, such as magnetic single crystals wi...     

Tunneling Anisotropic Magnetoresistance in L1_0-MnGa Based Antiferromagnetic Perpendicular Tunnel Junction

We report on the tunneling anisotropic magnetoresistance in antiferromagnetic perpendicular tunnel junction consisting of L1_0-MnGa/FeMn/AlO_x/Pt grown on GaAs(001) substrates by molecular-beam epitaxy. The temperature-dependent perpendicular exchange bias effect reveals an exchange coupling between ferromagnetic L1_0-MnGa and antiferromagnetic FeMn. The rotation of antiferromagnetic spins in FeMn can be driven by perpendicularly magnetized L1_0-MnGa due to the exchange-spring effect at the interface and leads to roomtemperature tunneling anisotropic magnetoresistance ratio of 0.86%. We also find that the tunneling anisotropic magnetoresistance strongly depends on temperature and angle. These results have broadened the material selection range for high performance antiferromagnetic spintronic devices.     

Effects of Monopolar Resistive Switching in Thin Diamond-Like Carbon Layers

JETP Letters - The current-voltage characteristics have been studied for Pt/diamond-like C/Pt structures based on thin (20 nm) diamond-like carbon layers, in which the ratio between carbon phases...     

Dynamic Backscattering Halo of Pulsed Laser Beams in Thin Cloud Layers

Radiophysics and Quantum Electronics - We consider the effect of the dynamic backscattering halo of pencil beams of light in thin layers of scattering media. Numerical modeling, which immediately...     

Optical Dimensional Phenomena in Thin Layers of Gold and Atomic Semiconductors

We have investigated optical dimensional phenomena which are manifested as the thickness dependences of the indices of refraction n and absorption k and of the magnitude of the quasiBrewster angle of thin layers of gold. In the range of thicknesses 20 < d > 180 , all these phenomena have an oscillating character. Based on the earlier published experimental data on the energy coefficients of transmission T and reflection R of thin layers of atomic semiconductors (Se, Te, Ge, and Si), new calculations of the thickness dependences of n and k have been carried out without the simplifying assumptions which lead to incorrect results. The errors in determining the optical constants of thin layers from photometric data have been analyzed in detail. The causes of the earlier errors in works devoted to this kind of investigation have been established.     

Oscillating Dependence of the Acoustic Attenuation Coefficient in Thin Metal Layers

Dimensional and frequency dependences of the energy absorption coefficient of a longitudinal sound wave in a plane parallel metal layer are theoretically investigated for arbitrary relationship between the layer thickness d and the electron free path l. Exact and asymptotic (for thick (d >> l) and thin (d << l) metal layers) formulas are derived for the coefficient for an arbitrary angular dependence of the probability of specular reflection of charge carriers from the sample surface q(). A square-root dependence of the acoustic absorption coefficient on the thin film thickness is predicted. If the direction of sound wave propagation is perpendicular to the thin metal layer boundary, the acoustic absorption coefficient becomes an oscillating function of the layer thickness; its amplitude decreases with increasing kd, where k is the acoustic wave number.     

Contribution from Moldcular Field to the Temperature Dependence of Tunneling Magnetoresistance

This paper presents a method that restrains a systematical behavior by a synchronistical measure and forces it to repeat a section of chaotic trajectory periodically, so that the high periodic chaotic signal can be obtained. The obtained signal not only keeps the typical features of the chaotic signal but also has the advantages of a periodic signal. The results of the simulation calculation, the experimental circuit and the experimental results about realizing the method on the basis of. Lorenz mode are given. The advantages of this method for applications in secret communication or covering information are discussed.     

Anisotropic Strange Star in 5D Einstein-Gauss-Bonnet Gravity

In this paper, we investigated a new anisotropic solution for the strange star model in the context of 5D Einstein-Gauss-Bonnet (EGB) gravity. For this purpose, we used a linear equation of state (EOS), in particular pr=βρ+γ, (where β and γ are constants) together with a well-behaved ansatz for gravitational potential, corresponding to a radial component of spacetime. In this way, we found the other gravitational potential as well as main thermodynamical variables, such as pressures (both radial and tangential) with energy density. The constant parameters of the anisotropic solution were obtained by matching a well-known Boulware-Deser solution at the boundary. The physical viability of the strange star model was also tested in order to describe the realistic models. Moreover, we studied the hydrostatic equilibrium of the stellar system by using a modified TOV equation and the dynamical stability through the critical value of the radial adiabatic index. The mass-radius relationship was also established for determining the compactness and surface redshift of the model, which increases with the Gauss-Bonnet coupling constant α but does not cross the Buchdahal limit.     

Anisotropic exchange interactions in CuTe2O5

Electron paramagnetic resonance (EPR) was used to study CuTe₂O₅ single crystals at frequencies of 9.4 and 160 GHz. Analytic expressions for the second and fourth moments of the EPR line are deduced with inclusion of the difference between the exchange couplings of the copper spin with its different neighbors. From comparing the calculated and measured EPR linewidths, the positions of copper ions with the strongest exchange interactions are identified. The parameters of the anisotropic exchange interaction between copper ions in a pair are found. The parameter of the exchange interaction between magnetically nonequivalent copper centers is determined from the frequency dependence of the EPR linewidth. The directions of the principal axes of the g tensors are established. The data obtained count in favor of a quasi-one-dimensional model of magnetism in CuTe₂O₅.     

Anisotropic solutions in the 5D space-time-mass theory

In this paper we present anisotropic families of cosmological solutions in the 5-dimensional space-time-mass theory of gravity. In particular, the 5D analogue of the Kasner solution of General Relativity is obtained. Some comments are given on the solutions.     

Optoelectronic Properties and Molecular Ordering of Tetracene Thin Layers on Gold

Fourier transform infrared (FTIR) spectroscopy and scanning tunneling microscopy (STM) were used to study the molecular organization and morphology of vacuum-deposited tetracene layers. FTIR and optical measurements confirm that tetracene molecules are not dissociated during vacuum thermal deposition. With STM imaging, a highly ordered, closely packed, lamella-like structure of tetracene monolayer film on the Au(111) surface was observed. Electroluminescence from the nanocomposite consisting of Au nanoparticles and tetracene film is concentrated within submicron luminescent centers and occurs at voltages of 4–5 V in a superlinear section of conduction current–voltage curves. The results can be useful for the design of planar light-emitting devices.     

Instantaneous Speckle-Modulated Interference Images and Coherent Effects in Optical Microscopy of Thin Layers

Optics and Spectroscopy - We consider the formation of instantaneous speckle-modulated interference images of thin transparent layers in an optical microscope under their illumination of either...