Influence of Ga^+ ion irradiation on thermal relaxation of exchange bias field in exchange-coupled CoFe/IrMn bilayers

This paper reports that the CoFe/IrMn bilayers are deposited by magnetron sputtering on the surfaces of thermallyoxidized Si substrates. It investigates the thermal relaxations of both non-irradiated and Ca^＋ ion irradiated CoFe/IrMn bilayers by means of holding the bilayers in a negative saturation field. The results show that exchange bias field decreases with the increase of holding time period for both non-irradiated and Ca^＋ ion irradiated CoFe/IrMn bilayers. Exchange bias field is also found to be smaller upon irradiation at higher ion dose. This reduction of exchange bias field is attributed to the change of energy barrier induced by ion-radiation.

Influence of temperature on thermal relaxation of exchange bias field in CoFe/Cu/CoFe/IrMn spin valve

A multilayered spin valve film with a structure of Ta(5 nm)/Co_(75)Fe_(25)(5 nm)/Cu(2.5 nm)/Co_(75)Fe_(25)(5 nm)/Ir_(20)Mn_(80)(12 nm)/Ta(8 nm)is prepared by the high-vacuum direct current(DC)magnetron sputtering.The effect of temperature on the spin valve structure and the magnetic properties are studied by x-ray diffraction(XRD),atomic force microscopy(AFM),and vibrating sample magnetometry.The effect of temperature on the exchange bias field thermomagnetic properties of multilayered spin valve is studied by the residence time of samples in a reverse saturation field.The results show that as the temperature increases,the IrMn(111)texture weakens,surface/interface roughness increases,and the exchange bias field decreases.Below 200℃,the exchange bias field decreases with the residence time increasing,and at the beginning of the negative saturation field,the exchange bias field Hex decreases first quickly and then slowly gradually.When the temperature is greater than 200℃,the exchange bias field is unchanged with the residence time increasing.

Thermal relaxation of exchange bias field in an exchange coupled CoFe/IrMn bilayer

This paper reports that a CoFe/IrMn bilayer was deposited by high vacuum magnetron sputtering on silicon wafer substrate; the thermal relaxation of the CoFe/IrMn bilayer is investigated by means of holding the film in a negative saturation field at various temperatures. The exchange bias decreases with increasing period of time while holding the film in a negative saturation field at a given temperature. Increasing the temperature accelerates the decrease of exchange field. The results can be explained by the quantitative model of the nucleation and growth of antiferromagnetic domains suggested by Xi H Wet al. [2007 Phys. Rev. B 75 014434], and it is believed that two energy barriers exist in the investigated temperature range.

Analysis of thermal responses in a two-dimensional porous medium caused by pulse heat flux

In this article, the generalized model for thermoelastic waves with two relaxation times is utilized to compute the increment of temperature, the displacement components, the stress components, and the changes in the volume fraction field in a two-dimensional porous medium. By using the Fourier-Laplace transform and the eigenvalue method, the considered variables are obtained analytically. The derived approach is estimated with numerical outcomes which are applied to the porous media with a geometrical simplification. The numerical results for the considered variables are performed and presented graphically. Finally, the outcomes are represented graphically to display the difference among the classical dynamical(CD) coupled, the Lord-Shulman(LS), and the Green-Lindsay(GL) models.

Thermoelastic Damping in Auxetic Plate

The paper deals with the thermoelastic damping in a rectangular auxetic plate during its free and forced vibrations.Contrary to existing descriptions the relaxation properties of the thermal field as well as the negative material(auxetic-material of negative Poisson′s ratio)properties are taken into considerations.

DYNAMIC RESPONSE OF TWO-DIMENSIONAL GENERALIZED THERMOELASTIC COUPLING PROBLEM SUBJECTED TO A MOVING HEAT SOURCE

Based on the Lord and Shulman generalized thermoelasticity theory with one relaxation time, an isotropic semi-infinite plate subjected to a moving heat source has been studied by employing the finite element method directly in time domain, whose distributions of nora dimensional temperature, displacement and stress are illustrated graphically. The results show that the present method is an effective and exact numerical one for solving the thermoelastic coupling problem and is capable of overcoming the defects of traditional integrated transformation and inverse integrated transformation methods. At the same time, the temperature step of the thermal wave front is obtained exactly in contrast with conventional numerical transformation methods.

Mathematical Modelling and Analysis of Lamb Waves in Elasto-Thermodiffusive Plates

The propagation characteristics of elasto-thermodiffusive Lamb waves in a homogenous isotropic,thermodiffusive,elastic plate have been investigated in the context of linear theory of generalized thermodiffusion.After developing the formal solution of the mathematical model consisting of partial differential equations,the secular equations have been derived by using relevant boundary conditions prevailing at the surfaces of the plate for symmetric and asymmetric wave modes in completely separate terms.The secular equations for long wavelength and short wavelength waves have also been deduced and discussed.The amplitudes of displacement components,temperature change and mass concentration under the Lamb wave propagation conditions have also been obtained.The complex transcendental secular equations have been solved by using a hybrid numerical technique consisting of irreducible Cardano method along with function iteration technique after splitting these in a system of real transcendental equations.The numerically simulated results in respect of phase velocity,attenuation coefficient,specific loss factor and relative frequency shift of thermoelastic diffusive waves have been presented graphically in the case of brass material.

ANALYTICAL SOLUTIONS OF NON-FOURIER PENNES AND CHEN-HOLMES EQUATIONS

The analytical solutions of non-Fourier Pennes and Chen Holmes equations are obtained using the Laplace transformation and particular solution method in the present paper. As an application, the effects of the thermal relaxation time % the blood perfusion wb, and the blood flow velocity v on the biological skin and inner tissue temperature T are stxldied in detail The results obtained in this study provide a good alternative method to study the bio-heat and a biophysical insight into the understanding of the heat transfer in the biotissue.