Effect Of Uniaxial Anisotropy Research Articles

The phase diagrams and the magnetic properties of a ternary mixed ferrimagnetic nanowire

A hexagonal nanowire consisting of a ferromagnetic spin-12 core, spin-1 inter core/shell and spin-32 outer shell coupled with ferrimagnetic interlayer couplings has been studied by the use of Monte Carlo simulation based on the heat bath algorithm. The exchange interactions and the uniaxial anisotropy effects on the magnetic properties of the system have been discussed. We found that, the system exhibits the compensation phenomenon, the first and the second order transitions. Moreover, we have obtained that, the existence of the tricritical point depend on the surface shell interaction.

Magnetic anisotropy and conical phase transition in monoaxial chiral magnets

Magnetic anisotropies in chiral spin systems can affect dramatically the allowed stable magnetic configurations. Using a Green's function approach, we examine the role of fluctuations in determining boundaries between allowed states in a monoaxial chiral magnet. The effects of uniaxial anisotropy are found to be most pronounced near the point separating the helicoidal, ferromagnetic, and paramagnetic phases. The cone state, which can appear when an external magnetic field is applied, is particularly strongly affected near the boundary with the paramagnetic phase. A metastable region is found, indicating the appearance of a fluctuation-induced phase transition. This metastable region arises from off-diagonal elements in the Green's functions, and can exist even without anisotropy.

Uniaxial anisotropy variations and the reduction of free layer coercivity in MnIr-based top spin valves

The effect of uniaxial anisotropy on the free layer coercivity has been studied on a MnIr-based top spin valve. Annealing and micro-patterning were applied to modify the anisotropy field. The anhysteretic magnetoresistance on magnetic field dependence has been obtained.

Spectral Domain Analysis of Resonant Characteristics of High Tc Superconducting Rectangular Microstrip Patch Printed on Isotropic or Uniaxial Anisotropic Substrates

In this paper, radiation characteristics of the perfectly superconducting, or an imperfectly conducting rectangular microstrip, which is printed on isotropic or uniaxial anisotropic substrate are investigated using a Fourier transforms domain in conjunction with the stationary phase method. The effects of uniaxial anisotropy on the resonant frequency, half-power bandwidth, and radiation patterns are investigated as the function of anisotropy ratio values of substrate materials. It is found that the resonant frequency and the half-power bandwidth are affected significantly by the superconductivity property of the patch. Further results show that a thin superconductor patch has a significant effect on the radiation pattern. Results are compared with previously published data and are found to be in good agreement.

Uniaxial anisotropy effects in the mixed-spin Ising model on a decorated Bethe lattice

The ferrimagnetic mixed-spin Ising model on a decorated Bethe lattice with the coordination number q, consisting of three kinds of magnetic atoms, is exactly solved here. We mainly analyze the critical temperature curves and the sub-lattice and total magnetization curves in this model. The effect of uniaxial single-ion anisotropy acting on two different kinds of decorated atoms and next-nearest-neighbor interaction is taken into account in particular. It has been found that the critical temperature versus uniaxial single-ion anisotropy dependence is not a monotonically increasing function for some chosen parameters. And there is also a reentrant phase transition with the coordination number q equal to 4 in the narrow region of the uniaxial single-ion anisotropy.

Analysis of HighTcSuperconducting Rectangular Microstrip Patches over Ground Planes with Rectangular Apertures in Substrates Containing Anisotropic Materials

A rigorous full-wave analysis of highTcsuperconducting rectangular microstrip patch over ground plane with rectangular aperture in the case where the patch is printed on a uniaxially anisotropic substrate material is presented. The dyadic Green’s functions of the considered structure are efficiently determined in the vector Fourier transform domain. The effect of the superconductivity of the patch is taken into account using the concept of the complex resistive boundary condition. The accuracy of the analysis is tested by comparing the computed results with measurements and previously published data for several anisotropic substrate materials. Numerical results showing variation of the resonant frequency and the quality factor of the superconducting antenna with regard to operating temperature are given. Finally, the effects of uniaxial anisotropy in the substrate on the resonant frequencies of different TM modes of the superconducting microstrip antenna with rectangular aperture in the ground plane are presented.

Resonant Frequency of Air Gap Tuned Circular Microstrip Antenna with Anisotropic Substrate and Superstrate Layers

Resonant frequency characteristics of air gap tuned circular microstrip antenna with uniaxially anisotropic substrate and superstrate layers is analysed in Hankel Transform domain using recursive equivalent circuit modelling. The effects of uniaxial anisotropy on the resonant frequency are investigated as the function of anisotropy ratio values of substrate and superstrate materials. According to the results, resonant frequency of anisotropic antenna exhibits incremental or decremental shifts with respect to isotropic one due to adjustment of the layer anisotropies and the thickness of the air gap. Thus, it is important to properly adjust layer anisotropies of the circular disk microstrip antenna for its efficient operation in microwave and communication systems applications.

Resonant frequency of a rectangular patch antenna using asymptotic basis functions

PurposeThe purpose of this paper is to illustrate three types of basis functions and their asymptotic forms defined over the patch to model the unknown currents.Design/methodology/approachA rigorous calculation of a microstrip structure that contains isotropic and anisotropic substrates via Galerkin's method is presented. The dyadic Green's functions of the problem are efficiently determined by the (TM, TE) representation.FindingsThe resonant frequency of a rectangular microstrip patch antenna using these different asymptotic basis functions is investigated. The effect of uniaxial anisotropy in the resonant frequency is presented for these asymptotic currents.Originality/valueComparisons are made, and show that the utilization of the asymptotic basis function provides a significant improvement in the computation time over the exact form in the evaluation of the resonant frequency of a microstrip patch antenna. Convergent solutions are in good agreement with the exact sinusoid basis function without edge condition and with those obtained from literature.

Effects of the resistive patch and the uniaxial anisotropic substrate on the resonant frequency and the scattering radar cross section of a rectangular microstrip antenna

The moment method technique is developed to examine the scattering properties of a rectangular microstrip patch antenna with non zero surface impedance. The boundary condition for the electric field is used to derive an integral equation for the electric current. The necessary terms for representing the surface resistance on the patch are derived and included in the integral equation in the form of a resistance matrix. The scattering radar cross section (RCS) of a microstrip antenna, including the effect of the surface resistance and the effect of a uniaxial substrate, is analysed. Effects of uniaxial anisotropy in the substrate on the complex resonant frequency of the microstrip patch antenna are also investigated. Numerical results show that the surface resistance significantly affects the RCS and radiation of the rectangular microstrip patches. Moreover, it is shown that the permittivity ε z has a stronger effect on the resonant frequency, the radiation and the scattering radar cross section than the permittivity ε x . It is worth noting that our calculated frequencies do not depend on the surface resistance.

A numerically efficient full-wave analysis of a tunable rectangular microstrip patch

A full-wave analysis for determining the resonant frequency and half-power bandwidth of a rectangular microstrip antenna with an air gap is presented. To make the study more general and valid for various antennas structures; during the theoretical formulation the metallic patch is assumed to be embedded in a multilayered media containing isotropic and/or uniaxial anisotropic dielectrics. The proposed method for determining the Green's function leads to a concise form of this, expressed in terms of a 4 × 4 matrix multiplication, which is easily implemented. Using Galerkin's method in solving the integral equation numerically, the complex resonant frequency of the microstrip antenna with an air gap is studied with sinusoidal functions as basis functions, which show fast numerical convergence. The numerical results for Galerkin's method and experiments are in good agreement. The air gap tuning effect on the resonant frequency and half-power bandwidth is investigated. Finally, numerical results for the effects of uniaxial anisotropy in the substrate on the operating frequency of the rectangular microstrip antenna with an air gap are also presented.

Penetration of the magnetic field into anisotropic superconducting particles

The effect of uniaxial anisotropy upon penetration of the magnetic field into superconducting particles of a spherical shape has been studied within the London theory. At the low temperatures in the case of strong anisotropy the penetration of the magnetic field is governed by the largest penetration depth determined by the currents normal to the layers.

Resonance of a rectangular microstrip patch on a uniaxial substrate

Effects of uniaxial anisotropy in the substrate on the complex resonant frequency of the microstrip patch antenna are investigated in terms of an integral equation formulation. The complex resonant frequency of the microstrip patch antenna is calculated using Galerkin's method to solve the integral equation. The sinusoidal functions that are selected as the basis functions, which show fast numerical convergence. Numerical results indicate that both the resonant frequency and the half-power bandwidth are increased due to positive uniaxial anisotropy and decreased due to negative uniaxial anisotropy. >

Uniaxial anisotropy effects on crosspolarisation level of printed dipole in superstrate-substrate configuration

The uniaxial anisotropy effects on the crosspolarisation level (CPL) of a printed dipole in the superstrate-substrate configuration are investigated. It is shown that the substrate anisotropy is more relevant than that of the cover, and is an important parameter to be considered in the design of a low CPL dipole array.

Electromagnetic scattering by a uniaxially anisotropic sphere

The problem of electromagnetic scattering by a uniaxially anisotropic sphere is studied for both dielectric and absorbing cases. The fields of the TM ro ř wave inside a uniaxial sphere can be derived to be expressed in series of Bessel functions, as in the isotropic case, but with the order of function determined by the anisotropic ratio (AR = εθ/εr). For the TE to ř wave, the uniaxial medium can be treated as an isotropic material characterised by εθ only, which is the permittivity parallel to the boundary surface of the medium. Wave propagation is not affected by the f directed permittivity. The effects of uniaxial anisotropy on the radar cross section (RCS) are also considered. It is found that the uniaxial anisotropy greatly influences the scattering behaviour of a spherical dielectric object. For an absorbing sphere, however, the uniaxial anisotropy no longer plays a significant role as in a dielectric sphere, and the dependance of the RCS on uniaxial anisotropy is found to be predictable. Details of theoretical treatment and numerical results are presented.

Anisotropy effects on pattern selection near dynamical instabilities

The effect of uniaxial anisotropy on the pattern selection mechanisms in driven systems is discussed within the framework of amplitude equations for the order parameter-like variable. It is shown, in a case where the dynamics admits a Lyapunov functional, how polygonal patterns are destabilized for constant and time-dependent anisotropy.

Effects of uniaxial anisotropy on the Curie temperature of the Heisenberg ferromagnet with mixed spins

For the Heisenberg ferromagnets with mixed spins ( S = 1 2 , S = 3 2 ) and ( S = 1 2 , S = 2 ), the effect of uniaxial anisotropy on the Curie temperature has been calculated by the use of the pair model approximation and its effect is shown to be significant for the mixed spin system ( S = 1 2 , S = 2 ).

Green's Function Approach for High‐Temperature Ferromagnetic Systems in the Presence of Uniaxial Anisotropy

AbstractThe effect of uniaxial anisotropy on the transition temperature for a ferromagnetic spinone system is investigated using the double time Green's function technique. The calculations are carried out up to the second order in the exchange coupling and exactly in the anisotropy term. The localized and the static correlations used in the formulation are calculated selfconsistently. The calculation is compared with corresponding results for an ordered system, which predicts an effective reduction in Tc with anisotropy in high temperature crystalline magnetic systems.