An irreversible Stirling heat pump cycle using FERROMAGNETIC MATERIALs as a cyclic working substance is established. The influences of finite-rate heat transfer, heat leak, regeneration time, regenerative loss and the internal irreversibility on the cyclic performance of magnetic heat pumps are taken into account. On the basis of the thermodynamic properties of FERROMAGNETIC MATERIALs, the performance characteristic of the FERROMAGNETIC Stirling heat pump cycle is investigated. Also, by applying the optimization technology, the relation between the optimal heating load and the coefficient of performance (COP) is derived. Furthermore, the maximum heating load and the corresponding COP as well as the maximum COP and the corresponding heating load are determined and discussed in detail. The results obtained in the present paper may provide some new information for the optimal design and the development of real magnetic heat pumps.

Using the transfer-matrix method, Spin transport in FERROMAGNETIC bilayer graphene superlattice, which can be realized by putting a series of FERROMAGNETIC insulator layers on top of a bilayer grapheme is studied. The FERROMAGNETIC layers with exchange energy Eex are in contact with gate of potential energy V0. It is considered that the magnetization in the two FERROMAGNETIC layers are aligned parallel (P) and antiparallel (AP) to each other. The spin transmissions probability (T­ and T¯) and the spin conductance (G­ and G¯) are studied. The spin polarization is calculated through the spin conductance. The total conductance (Gpq and GAPq) is also considered. It is found that perfect reflection can occur at normal incident, i.e., T­=T= 0. The spin conductance and the swpin polarization are found to exhibit oscillatory depending on the barrier height. The highest value of oscillating amplitude for SP% can rich 100% or (-100%) under special condition.

Introduction: Structural and magnetic properties of FERROMAGNETIC Fe thin layer films on Si substrates have been reported. We present topography features of these nanostructures films by atomic force microscopy (AFM). Characterization of magnetic domains and walls between them can be performed by using magnetic force microscopy (MFM) and alternating gradient field magnetometer (AGFM) instruments. The Fe thickness ranges from 50 to 150 nm. Our focus is to study systematically the effects of film thickness on magnetic anisotropy in thin films grown on semiconductor substrates. MFM images reveal stripe domain structure for the 100nm thick Fe on Si as well as hysteresis curves. The effective anisotropy shows oscillation for two types of Si substrates when the Fe films thickness increased.Aim: Our focus is to investigate systematically the effect of film thickness on magnetic hysteresis and effective anisotropy, especially in thin films grown on semiconductors substrates. For revealing stripe domain structure of Fe/Si (100) and Fe/Si (111), we use MFM pictures as well as hysteresis curves.MATERIAL and method: Fe thin films were deposited by thermal evaporation. Iron ingots from a 99.99 % purified Fe powder evaporated using an electron gun. The deposited Fe layer thicknesses vary from 50 to 150 nm. The crystalline structure of the deposited structures, X-ray diffraction method was used for investigation of nanostructure. Magnetic properties were also measured with MFM and experimental hysteresis loops were obtained by AGFM unit.Results: For Fe layer with 50nm thickness, Fe on Si (100) and Si (111) substrates, the Fe grows with (110) texture and has a bcc structure. The coercive field measured for the Fe films is about 100Oe. The measured hysteresis loops show that the coercive field decreases while the saturation field increases and such uniaxial anisotropy increases with increasing step density.Conclusion: Hysteresis diagrams show good FERROMAGNETIC characteristics of these samples. The effective anisotropy shows oscillation, for two substrates Si types, when the Fe films thickness increased.

This study presents critical buckling of functionally graded soft FERROMAGNETIC porous (FGFP) rectangular plates, under magnetic field with simply supported boundary condition. Equilibrium and stability equations of a porous rectangular plate in transverse magnetic field are derived. The geometrical nonlinearities are considered in the Love- Kirchhoff hypothesis sense. The formulations are compared to those of homogeneous isotropic plates were given in the literature. In this paper the effect of pore pressure on critical magnetic field of plate and the effect of important parameters of poroelastic MATERIAL on buckling capacity are investigated. Also the compressibility of fluid and porosity on the buckling strength are studied.