Third Order Perturbed Energy of Cobalt Ferrite Thick Films

Magnetic properties and easy axis orientation of cobalt ferrite films with applied magnetic field and number of layers were studied. According to our theoretical studies explained in this manuscript, the magnetically easy and hard directions of cobalt ferrite films solely depend on in plane and out of plane magnetic fields. According to 3-D and 2-D plots, there are many easy and hard directions at one particular value of in plane or out of plane magnetic field. The magnetic properties were investigated for cobalt ferrite films with thickness up to 10,000 unit cells. The total magnetic energy was calculated for a unit spin of cobalt.Comment: 13 pages, 4 figure

Effect of demagnetization factor dependence on energy of ultra-thin ferromagnetic films with four layers

Simple cubic and body centered cubic ferromagnetic lattices with four layers were studied using Heisenberg Hamiltonian. According to 3-D plots, the films with four layers can be easily oriented in certain directions under the influence of particular demagnetization factor and angles for both sc(001) and bcc(001) ferromagnetic lattice structures. A flat part can be seen in the middle of 3-D plots in addition to periodic variations. When the demagnetization factor is given by =6, sc(001) film with four layers can be easily oriented in 0.6 radians direction for the energy parameter values used in this simulation. Under the influence of demagnetization factor given by =5.2 , thin film of bcc(001) lattice with four layers can be easily oriented along 0.63 radians direction.Comment: 12 pages, 4 figure

Optical properties of spin coated Cu doped ZnO nanocomposite films

Spin coating technique was used to synthesize pure ZnO and Cu doped ZnO films on amorphous and conducting glass substrates. The doped amount of Cu in ZnO was varied up to 5% in atomic percentage. Speed of spin coating system, coating time, initial chemical solution and annealing conditions were varied to optimize the properties of samples. Transmittance of samples was measured for ZnO doped with 1, 2, 3, 4 and 5% of Cu. Absorbance, reflectance and refractive index were derived from the measured transmittance. Film thickness of each film was calculated using the graphs of refractive index versus wavelength. Film thickness varies in a random manner depending on the amount of ZnO or Cu doped ZnO solutions spread on the substrate. The energy gap of each film was calculated using the graph of square of absorption coefficient time photon energy versus photon energy. The calculated energy gap values of Cu doped ZnO film samples decrease with the Cu concentration in ZnO. This means that the conductivity of ZnO can be increased by adding a trace amount of conducting material such as Cu.Comment: 14 pages, 5 figures, 2 table

Easy axis orientation of Strontium ferrite thin films described by spin reorientation

In plane orientation of magnetic easy axis of sputtered strontium hexaferrite thin films has been explained using classical Heisenberg Hamiltonian. The variation of average value of in plane spin component with temperature was plotted in order to determine the temperature at which easy axis is oriented in the plane of the strontium ferrite film. The average value of in plane spin component in this 2-D model reaches zero at one particular temperature. This particular temperature obtained using our theoretical model agrees with the experimental value of the temperature of rf sputtered polycrystalline strontium ferrite thin films deposited on polycrystalline Al2O3 substrates (500 0C). This spin reorientation temperature solely depends on the values of energy parameters used in our modified Heisenberg Hamiltonian equation.Comment: 9 pages, 5 figure

Easy Axis orientation of Ferromagnetic Films as Described by Third Order Perturbed Heisenberg Hamiltonian

The magnetic easy axis orientation was studied by the third order perturbed Heisenberg Hamiltonian. Ferromagnetic CoPt/AlN multilayer thin films with number of layers N=11, 16 and 21 synthesized on fused quartz substrates using dc magnetron sputtering technique have been employed as experimental data. According to experimental research performed by some other researchers, easy axis of these fcc structured ferromagnetic films is oriented in the plane of the film at one particular temperature. Average value of out of plane spin component was plotted against temperature in order to determine the spin reorientation temperature. The spin reorientation temperature was highly sensitive to 2nd order magnetic anisotropy constant.Comment: 9 pages, 3 figure

Classical Heisenberg Hamiltonian Solution of Oriented Spinel Ferrimagnetic Thin Films

The classical Heisenberg Hamiltonian was solved for oriented spinel thin and thick cubic ferrites. The dipole matrix of complicated cubic cell could be simplified into the form of dipole Matrix of simple cubic cells. This study was confined only to the highly oriented thin films of ferrite. The variation of total energy of Nickel ferrite thin films with angle and number of layers was investigated. Also the change of energy with stress induced anisotropy for Nickel ferrite films with N=5 and 1000 has been studied. Films with the magnetic moments ratio 1.86 can be easily oriented in 90 direction when N is greater than 400.Comment: 18-pages, 4-figures, 3-table

Demagnetization factor dependence of energy of thick ferromagnetic films

Second order perturbed Heisenberg Hamiltonian was employed to study the variation of energy of ferromagnetic thick films with demagnetization factor. Under the influence of demagnetization factor given by =6.6, the sc(001) film with 10000 layers can be easily oriented in 0.6 radians direction for the values of energy parameters used in this report. Easy direction of thick fcc(001) film with 10000 layers was determined at 0.66 radians, when the demagnetization factor is given by =2.6. The energy of sc(001) thick film is larger than that of fcc(001) thick film. But the energy curve of fcc(001) thick film is smoother than that of sc(001).Comment: 8 pages, 4 figure

Photocurrent enhancement of spin coated CdS thin films by adding Cu

Cu added CdS films were synthesized using spin coating technique at different spin speeds for different time durations. Films were subsequently annealed at different temperatures for different time periods in air to crystallize the phase of CdS in thin film form. Films were characterized using XRD, UV- visible spectrometer and solar simulator. According to XRD patterns, addition of trace amount of Cu did not change the structure of CdS. However, the optical band gap gradually decreases with percentage of Cu as expected. As a result, the photocurrent, fill factor and efficiency measured in KI/I2 electrolyte gradually increase with the amount of Cu. Photovoltaic properties could be improved without altering the structure of CdS. Efficiency enhanced CdS films find potential applications in solar cell industry.Comment: 12 pages, 2 tables, 4 figure

Effect of annealing temperature on photovoltaic properties of spin coated CdS films

CdS thin film samples were fabricated using spin coating technique on normal glass and conductive glass substrates and annealed at different temperatures. According to the XRD patterns of films prepared on normal glass substrates, polycrystalline films are consist of single phase of CdS. Films synthesized on conductive glass substrates were employed for photovoltaic measurements. Variation of photovoltaic properties with annealing temperature was investigated. The liquid junction photocell was measured in the electrolyte of Na2S2O3/I2. Then, the short circuit photo current and open circuit photo voltage were measured at room temperature under illumination and under dark using a solar cell simulation system. Optical band gap of CdS film samples was determined by measuring UV-visible spectroscopy.Comment: 14 pages, 4 figures, 4 table

Magnetic Dipole Interaction and Total Magnetic Energy of Lithium Ferrire Thin Films

The total magnetic energy of Lithium ferrite thin films was determined using the classical Heisenberg Hamiltonian. The short range magnetic dipole interactions between spins within one unit cell and the interactions between spins in two adjacent unit cells have been determined in order to find the total magnetic energy of lithium ferrite films. Only the spin pairs with separation less than cell constant have been taken into account to calculate dipole interaction and spin exchange interaction. Theoretically several easy and hard directions of lithium ferrite film were found for one set of energy parameters included in our modified Heisenberg Hamiltonian. The dependence of total magnetic energy of a lithium ferrite film on number of unit cells, spin exchange interaction, dipole interaction, second order magnetic anisotropy, fourth order magnetic anisotropy, internal applied magnetic field and stress induced magnetic anisotropy has been explained in this manuscript.Comment: 10 pages, 3 figures, 2 table