Isfahan University of Technology, The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 8 3 2019 11 26 Preparation and investigation of bulk and thin film samples of strontium ferrite Preparation and investigation of bulk and thin film samples of strontium ferrite 119 128 772 FA A Poorbafrani P Kameli H Salamati Journal Article 2019 11 26   In this article, bulk and thin film samples of strontium ferrite have been studied. Due to the high electrical resistivity in strontium ferrite, energy loss due to eddy currents reduces and because of this, it can be used in high frequency magnetic circuits. On the other hand, strontium ferrite has attracted much attention as a permanent magnet. At first, we study the preparation process of bulk samples of strontium ferrite by a solid state reaction technique. In preparation of samples, to optimize the magnetic properties, we have used the stoichiometry factor (n = Fe2O3 / SrO) of 5.25. In addition, we have used additives such as CaO and SiO2 to control grain growth. The samples have been prepared in two series: Isotropic and Anisotropic. For preparation of anisotropic samples, the magnetic field of 1T has been used for orientation of the grains during the press. Then, X-ray diffraction, Scanning Electron Microscopy (SEM), EDAX analysis and Magnetometer, was used for analyzing and comparing of structural and magnetic properties of isotropic and anisotropic samples. The results indicate that, due to the applied magnetic field, the structural and Magnetic properties of anisotropic samples improved efficiently because of the orientation of the grains during the press. In the next stage, we used bulk samples to prepare strontium ferrite thin films by Pulsed Laser Deposition technique (PLD). The Si (111) substrate has been used to prepare the thin films. Then we have studied the microstructure of thin films by X-ray diffraction, SEM and EDAX analysis. These studies on different samples show that for the preparation of crystalline phase of strontium ferrite thin films, the substrate temperature must be higher than 800˚C. The optimum conditions for preparation of strontium, ferrite thin films have been achieved on the substrate temperature of 840˚C and oxygen pressure of 75 mtorr.   In this article, bulk and thin film samples of strontium ferrite have been studied. Due to the high electrical resistivity in strontium ferrite, energy loss due to eddy currents reduces and because of this, it can be used in high frequency magnetic circuits. On the other hand, strontium ferrite has attracted much attention as a permanent magnet. At first, we study the preparation process of bulk samples of strontium ferrite by a solid state reaction technique. In preparation of samples, to optimize the magnetic properties, we have used the stoichiometry factor (n = Fe2O3 / SrO) of 5.25. In addition, we have used additives such as CaO and SiO2 to control grain growth. The samples have been prepared in two series: Isotropic and Anisotropic. For preparation of anisotropic samples, the magnetic field of 1T has been used for orientation of the grains during the press. Then, X-ray diffraction, Scanning Electron Microscopy (SEM), EDAX analysis and Magnetometer, was used for analyzing and comparing of structural and magnetic properties of isotropic and anisotropic samples. The results indicate that, due to the applied magnetic field, the structural and Magnetic properties of anisotropic samples improved efficiently because of the orientation of the grains during the press. In the next stage, we used bulk samples to prepare strontium ferrite thin films by Pulsed Laser Deposition technique (PLD). The Si (111) substrate has been used to prepare the thin films. Then we have studied the microstructure of thin films by X-ray diffraction, SEM and EDAX analysis. These studies on different samples show that for the preparation of crystalline phase of strontium ferrite thin films, the substrate temperature must be higher than 800˚C. The optimum conditions for preparation of strontium, ferrite thin films have been achieved on the substrate temperature of 840˚C and oxygen pressure of 75 mtorr. strontium ferrite stoichiometry structural and magnetic properties Pulsed Laser Deposition (PLD)
Isfahan University of Technology, The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 8 3 2019 11 26 Calculation of the effect of neutrinos on the protoneutron star structure Calculation of the effect of neutrinos on the protoneutron star structure 129 136 773 FA GH Bordbar B Khosropour Journal Article 2019 11 26   In this paper, we consider the first case of formation of newborn neutron star named protoneutron star which is described with constant entropy per baryon about 1-2kB ( kB is Boltzman constant ) and lepton fraction about 0.3-0.4. In this case, by considering the neutrinos mean energy in our calculations, we compute the total energy, equation of state, mass and radius of protoneutron star. Finally, for different entropies and lepton fractions, we compare our results with the case in which the neutrinos effect is ignored.   In this paper, we consider the first case of formation of newborn neutron star named protoneutron star which is described with constant entropy per baryon about 1-2kB ( kB is Boltzman constant ) and lepton fraction about 0.3-0.4. In this case, by considering the neutrinos mean energy in our calculations, we compute the total energy, equation of state, mass and radius of protoneutron star. Finally, for different entropies and lepton fractions, we compare our results with the case in which the neutrinos effect is ignored. protoneutron star neutrinos structure
Isfahan University of Technology, The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 8 3 2019 11 26 Study of the fission process of deformed Na clusters in liquid-drop stabilized jellium model Study of the fission process of deformed Na clusters in liquid-drop stabilized jellium model 137 141 774 FA M Payami B Shakeri Journal Article 2019 11 26   In this work, using the liquid drop model in the context of the stabilized jellium model, we have studied the fission of charged Na clusters. In this study we have assumed a deformed non-spherical shape for the cluster. The ground state energies, critical sizes, fission barrier height, and the evaporation energies have been calculated. The results show a better agreement to the experimental results compared to our earlier work.   In this work, using the liquid drop model in the context of the stabilized jellium model, we have studied the fission of charged Na clusters. In this study we have assumed a deformed non-spherical shape for the cluster. The ground state energies, critical sizes, fission barrier height, and the evaporation energies have been calculated. The results show a better agreement to the experimental results compared to our earlier work. liquid-drop model stabilized jellium model fission critical sizes fission barrier height evaporation energy
Isfahan University of Technology, The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 8 3 2019 11 26 Ab inito calculations of Hubbard parameters for NiO and Gd crystals Ab inito calculations of Hubbard parameters for NiO and Gd crystals 143 152 775 FA A. R Faghihi And S Jalali Asadabadi S Jalali Asadabadi Journal Article 2019 11 26   In this research the Hubbard parameters have been calculated for NiO and Gd crystals, as two strongly correlated systems with partially full 3d and 4f levels, respectively. The calculations were performed within the density functional theory (DFT) using the augmented plane waves plus the local orbitat (APW+lo) method. We constructed a suitable supercell and found that the Hubbard parameters for the NiO and Gd compounds are equal to 5.9 eV and 5.7 eV, respectively. Our results are in good agreement with experimental data and results of other computational methods. Then we used the obtained parameters to study the structural properties of NiO and Gd by means of LDA+U approximation. Our results calculated by the LDA+U method which are in better agreement with the experiment show a significant improvement compared to the GGA approximation. The result shows that our method for calculating U parameter can be considered as a satisfactory method to study a strongly correlated system.   In this research the Hubbard parameters have been calculated for NiO and Gd crystals, as two strongly correlated systems with partially full 3d and 4f levels, respectively. The calculations were performed within the density functional theory (DFT) using the augmented plane waves plus the local orbitat (APW+lo) method. We constructed a suitable supercell and found that the Hubbard parameters for the NiO and Gd compounds are equal to 5.9 eV and 5.7 eV, respectively. Our results are in good agreement with experimental data and results of other computational methods. Then we used the obtained parameters to study the structural properties of NiO and Gd by means of LDA+U approximation. Our results calculated by the LDA+U method which are in better agreement with the experiment show a significant improvement compared to the GGA approximation. The result shows that our method for calculating U parameter can be considered as a satisfactory method to study a strongly correlated system. DFT APW+lo Hubbard parameter (U) LDA+U
Isfahan University of Technology, The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 8 3 2019 11 26 The quantum dynamics of mesoscopic discrete-charge electric circuits The quantum dynamics of mesoscopic discrete-charge electric circuits 153 157 776 FA F Kheirandish H Pahlavan Journal Article 2019 11 26   The quantum dynamics of a charged particle in an infinite chain of single-state quantum wells, in tight-binding approximation and under the action of an arbitrary time-dependent external field is investigated. The connection between the Hamiltonian description of this model and the Hamiltonian of a discrete-charge mesoscopic quantum circuit is elucidated. Based on this connection, the persistent current on a L-design nondissipative circuit is obtained.   The quantum dynamics of a charged particle in an infinite chain of single-state quantum wells, in tight-binding approximation and under the action of an arbitrary time-dependent external field is investigated. The connection between the Hamiltonian description of this model and the Hamiltonian of a discrete-charge mesoscopic quantum circuit is elucidated. Based on this connection, the persistent current on a L-design nondissipative circuit is obtained. mesoscopic systems charge discreteness dynamical algebra
Isfahan University of Technology, The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 8 3 2019 11 26 Crystal structure and magnetic properties of RFe10V2Zy (R = Y, Nd and Z = H, N) Crystal structure and magnetic properties of RFe10V2Zy (R = Y, Nd and Z = H, N) 159 168 777 FA N Tajabor H Fadafan Khandan M R Alinejad Journal Article 2019 11 26   YFe10V2 and NdFe10V2 interstitially modified compositions with hydrogen and nitrogen atoms were prepared by solid – gas reaction and their structural and magnetic properties were studied. The XRD patterns indicate that the samples are single phase and better than 95% and their purity improves after hydrogenation. The crystallites were broken by nitrogenation which is due to the penetration of N atoms within Fe sites. In addition, easy magnetization direction corresponds to the tetragonal c-axis at room temperature. Thermomagnetic measurements illustrate that the 2-17 impurity phase is formed by annealing samples above 1000 ºC. Results of the dc-susceptibility measurements of NdFe10V2 sample exhibit a spin reorientation transition at TSR = 117 K. By analysis of the magnetization curves, first and second order anisotropy constants were deduced which gradually decreased by increasing temperature in the case of YFe10V2. But in the case of NdFe10V2, they tend to a maximum about 200 K and then follow natural thermal decrease.   YFe10V2 and NdFe10V2 interstitially modified compositions with hydrogen and nitrogen atoms were prepared by solid – gas reaction and their structural and magnetic properties were studied. The XRD patterns indicate that the samples are single phase and better than 95% and their purity improves after hydrogenation. The crystallites were broken by nitrogenation which is due to the penetration of N atoms within Fe sites. In addition, easy magnetization direction corresponds to the tetragonal c-axis at room temperature. Thermomagnetic measurements illustrate that the 2-17 impurity phase is formed by annealing samples above 1000 ºC. Results of the dc-susceptibility measurements of NdFe10V2 sample exhibit a spin reorientation transition at TSR = 117 K. By analysis of the magnetization curves, first and second order anisotropy constants were deduced which gradually decreased by increasing temperature in the case of YFe10V2. But in the case of NdFe10V2, they tend to a maximum about 200 K and then follow natural thermal decrease. magnetization magnetic anisotropy spin reorientation solid - gas reaction
Isfahan University of Technology, The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 8 3 2019 11 26 Mesons states and their dependence on spin and isospin Mesons states and their dependence on spin and isospin 169 175 778 FA A A Rajabi N Salehi Journal Article 2019 11 26   Meson is composed of one quark and one antiquark moving under the effect of confinement, oscillating and color potentials. Since quarks are particles with spin , there is a spin-spin interaction potential. Also we have isospins for u and d quarks and we can consider related potentials on isospin-isospin and spin-isospin effects. By comparing the given meson spectrum with the amount calculated in this model, it can be inferred that mesons quark-antiquark are in a state of singlet or triplet regarding spin and isospin. By using this model, the states of configuration spin-isospin of each meson can be calculated   Meson is composed of one quark and one antiquark moving under the effect of confinement, oscillating and color potentials. Since quarks are particles with spin , there is a spin-spin interaction potential. Also we have isospins for u and d quarks and we can consider related potentials on isospin-isospin and spin-isospin effects. By comparing the given meson spectrum with the amount calculated in this model, it can be inferred that mesons quark-antiquark are in a state of singlet or triplet regarding spin and isospin. By using this model, the states of configuration spin-isospin of each meson can be calculated mesons spectrum quark confinement potential color potential
Isfahan University of Technology, The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 8 3 2019 11 26 Fabrication of electrodeposited Ni-Cu/Cu multilayered films and study of their nanostructures before and after annealing Fabrication of electrodeposited Ni-Cu/Cu multilayered films and study of their nanostructures before and after annealing 177 182 779 FA I Kazeminezhad A Barati Journal Article 2019 11 26  In this work electrodeposited Ni-Cu/Cu metallic multilayered films with different thicknesses of Ni and Cu were prepared on (100) polycrystalline Cu substrates. The nanostructure of the multilayers was studied using XRD. The existence of satellite peaks in the XRD patterns showed that the multilayered films have superlattice structures. The difference between the intensity of ML(200) and ML(111) peaks showed that the multilayers have a strong texture of (100) as their substrate structures which confirms the epitaxial growth. The morphology of the films was studied by SEM. The SEM images showed that the surface of the films is rough. The samples were also analyzed using EDX and the results showed that the real content of Ni is less than its nominal content this refers to the current efficiency which is less than unity due to hydrogen evolution. In the second stage of the work some identical samples which have the highest order of satellite peaks were electrodeposited. The samples were annealed at different temperatures and times. Their structures were then studied by XRD. The XRD patterns of the annealed samples showed that if the temperature and time of annealing increase, the satellite peaks begin to disappear. It means by increasing these two parameters, the sharpness of the bilayer interface decreases and the multilayered structure tends to become alloy structure. The morphology of the samples was also studied by SEM. The SEM images showed that the surface of the annealed films becomes approximately uniform due to the diffusion of Ni and Cu atoms to Cu and Ni layers, respectively.  In this work electrodeposited Ni-Cu/Cu metallic multilayered films with different thicknesses of Ni and Cu were prepared on (100) polycrystalline Cu substrates. The nanostructure of the multilayers was studied using XRD. The existence of satellite peaks in the XRD patterns showed that the multilayered films have superlattice structures. The difference between the intensity of ML(200) and ML(111) peaks showed that the multilayers have a strong texture of (100) as their substrate structures which confirms the epitaxial growth. The morphology of the films was studied by SEM. The SEM images showed that the surface of the films is rough. The samples were also analyzed using EDX and the results showed that the real content of Ni is less than its nominal content this refers to the current efficiency which is less than unity due to hydrogen evolution. In the second stage of the work some identical samples which have the highest order of satellite peaks were electrodeposited. The samples were annealed at different temperatures and times. Their structures were then studied by XRD. The XRD patterns of the annealed samples showed that if the temperature and time of annealing increase, the satellite peaks begin to disappear. It means by increasing these two parameters, the sharpness of the bilayer interface decreases and the multilayered structure tends to become alloy structure. The morphology of the samples was also studied by SEM. The SEM images showed that the surface of the annealed films becomes approximately uniform due to the diffusion of Ni and Cu atoms to Cu and Ni layers, respectively. electrodeposition Ni-Cu/Cu multilayer ultra thin film annealing
Isfahan University of Technology, The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 8 3 2019 11 26 Electronic transport properties of carbon nanotube metal-semiconductor-metal Electronic transport properties of carbon nanotube metal-semiconductor-metal 183 183 780 FA F Khoeini H Farman Journal Article 2019 11 26  In this work, we study electronic transport properties of a quasi-one dimensional pure semi-conducting Zigzag Carbon Nanotube (CNT) attached to semi-infinite clean metallic Zigzag CNT leads, taking into account the influence of topological defect in junctions. This structure may behave like a field effect transistor. The calculations are based on the tight-binding model and Green’s function method, in which the local density of states(LDOS) in the metallic section to semi-conducting section, and muli-channel conductance of the system are calculated in the coherent and linear response regime, numerically. Also we have introduced a circuit model for the system and investigated its current. The theoretical results obtained, can be a base, for developments in designing nano-electronic devices.  In this work, we study electronic transport properties of a quasi-one dimensional pure semi-conducting Zigzag Carbon Nanotube (CNT) attached to semi-infinite clean metallic Zigzag CNT leads, taking into account the influence of topological defect in junctions. This structure may behave like a field effect transistor. The calculations are based on the tight-binding model and Green’s function method, in which the local density of states(LDOS) in the metallic section to semi-conducting section, and muli-channel conductance of the system are calculated in the coherent and linear response regime, numerically. Also we have introduced a circuit model for the system and investigated its current. The theoretical results obtained, can be a base, for developments in designing nano-electronic devices. carbon nanotubes electronic transport AC current