مجله فیزیک کاربردی
سال پنجم شماره 2 (پیاپی 9، پاییز و زمستان 1394)

Magnetic layers composed of soft ferromagnetic alloys as novel magnetic materials have been attracted great attention in recent years. These materials are suitable candidates for use in electronic circuits especially at high frequency microelectronics elements and magnetic sensors. In this paper, electronic transport properties under application of alternative current of magnetic thin wires with cylindrical geometry toward analysis of the magnetoimpedance (MI) effect will be studied. Our aim is to solve the Maxwell and Landau-Lifshitz equations simultaneously in cylindrical coordinate. Furthermore, we in addition are aiming investigation of magneto-dynamical equations of the mentioned structures under application of alternative magnetic fields with microwave frequencies. The main focus will be on the effect of exchange interaction term on the MI response which results in spin wave in resonance and anti-resonance effect addition to the wave propagation in such structures. Finally, based on the important parameters the MI response will be analyzed for application in magnetic sensors and microelectronics elements.

In 1964 a proposal was offered in this basis that all hadrons made from fundamental particles named “Quarks”. These particles are bounded in hadrons by “Gluons”. Ultimately scientists present the term of “confinement” as a new concept through their failures in producing a single quarks at laboratory. In this paper we analyze a confining quark by using AdS/CFT correspondence. According to holography we should analyze a classical string which is started from boundary and exist in confined bulked space. In AdS/CFT correspondence and confining background we consider a cut off in hologram dimension thus the string can’t reach infinite and get near to this cut off asymptotically. If we consider a pair of quark-antiquark with distance of L from each other on the boundary, we can say the stretched string is half of the flux tube among quarks. When we send the antiquark at infinite distance away, the string’s structure shows the flux tube direction. By comparing free and confining string in this paper we show that the string changed from being a straight line.

In this paper, electrochemical exfoliation of graphite was used for fabrication of graphene particles. By using XRD, structure of sample was confirmed. Then, powder of particles was pressed by press equipment and converted to a tablet. By placing the tablet in an electrical circuit, I-V curve for the tablet was measured. Resistance, resistivity, and electrical conductivity were measured by four probe system. The results showed that fabricated sample has graphene particles but there are a few amount of graphite structure as well which can be increased percentage of graphene with systematic method. Therefore, a simple and cheap method is introduced for fabrication of grapheme particles.

Due to the proper direct ban gap and high absorption coefficient of CuInS(CIS) absorber layer, this layers devoted much attention to itself. Beside of this, using of flexible substrates in solar cell fabrication, cause to increase the benefit of CIS usage. The solar cell based on CIS, due to their high conversion efficiency, their low cost potential and the many application possibilities are very attractive. They can be grown on metal or polymer substrate with a variety of deposition methods. The conversion efficiency depends on the choice of the substrates and of the processing technology. In this research, we prepare and characterize structural and optical properties of CIS absorber layers on Al and polymer as tow flexible substrate. As the results, by changing the substrate from Aluminum to Polymer, the crystalline size and strain of CIS layers were changed. These changes are probably related to coefficient of thermal expansion of Aluminum, polymer substrates and CIS layer. In addition, Aluminum substrate can decrease resistivity (increase conductivity) of CIS absorber layer.

In this paper, we study the size-dependent electronic conductance of a polyacetylene nanoring in the presence and absence of magnetic field by using Green’s function technique at the tight-binding approach. We consider two types of the nanoring that the number of single and double bonds in the possible paths for electron be or not be identical. The results show that the tunneling conductance in the gap region decreases exponentially and the number of peaks in the resonance region increases by increasing the length of the nanoring. By applying a magnetic field, the position of resonance peaks in the conductance spectrum shift and the tunneling conductance changes too. This means that for a nanoring with fixed length and in the presence of magnetic field, the tunneling conductance improves for the case that there is not bonding symmetry on the electron paths with respect to the absence of field. There is a vise-versa situation for the symmetric case.

Nitrogen doped zinc oxide (ZnO:N) thin films are synthesized on glass and pure ZnO buffer layer at 450 °C by spray pyrolysis method. The XRD spectra show the grown samples have polycrystalline nature in hexagonal phase while their preferred growth direction are changed. This affectness is clear in such a way that the transmittances of the layers are decreased and their absorbances are increased. These variations are well compatible with the variations in the crystallite size and also crystalline defect density in these materials. Electrical properties of the layers show a higher electrical conductivity in sample grown on ZnO buffer layer compared with other one which is grown on glass substrate.