arXiv subjects

P. Samarasekara

Publications and source records attributed to P. Samarasekara.

26 records · Page 2Linked to original sources

arXiv2016

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).

cond-mat.mtrl-sci↗

arXiv2016

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.

cond-mat.mes-hall↗

arXiv2016

Magnetic properties of Cobalt films described by second order perturbed Heisenberg Hamiltonian

Second order perturbed Heisenberg Hamiltonian was employed to investigate the magnetic properties of hexagonal Cobalt films. Initially the number of nearest neighbors and the constants arisen from the partial summation of the dipole interactions of the structure of cobalt were calculated using some special algorithms. Minimization of the energy difference between the easy and hard direction of a memory device is very important. When the energy difference between the easy and hard directions is significantly small, the magnetic moments in a memory device can be quickly rotated between easy and hard directions under the influence of a small magnetic field. The thickness of a cobalt film corresponding to this minimum energy difference calculated using this theoretical model agrees with some experimental data of cobalt based magnetic memory devices.

cond-mat.mes-hall↗

arXiv2016

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.

cond-mat.mes-hall↗

arXiv2016

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.

cond-mat.mtrl-sci↗

arXiv2016

Structural and electrical properties of CdS thin films spin coated on glass substrates

CdS samples were synthesized on amorphous glass and conductive glass substrates at room temperature using spin coating technique and subsequently annealed at five different temperatures in air for one hour. The speed and time of spin coating were varied initially to optimize the properties of the samples. FTIR spectroscopy was used in this experiment to analyze CdS bond formation variation with annealing temperature. A liquid junction photocell with KI/I2 electrolyte was prepared to measure the photovoltaic properties. Photovoltage, photocurrent and corresponding output power were measured in order to determine the output power.

cond-mat.mtrl-sci↗

arXiv2016

Magnetic energy of sc ferromagnetic films with three layers as described by third order perturbed Heisenberg Hamiltonian

The solution of third order perturbed Heisenberg Hamiltonian of simple cubic ferromagnetic ultra-thin films with three layers were found. All the magnetic energy parameters such as spin exchange interaction, magnetic dipole interaction, second order magnetic anisotropy, fourth order magnetic anisotropy, applied magnetic field, demagnetization factor and stress induced anisotropy were included in the third order perturbed Heisenberg Hamiltonian. 3-D plots of stress induced anisotropy, out of plane magnetic field, demagnetization factor and spin exchange interaction are presented in this manuscript. Magnetic easy and hard directions were determined using these 3-D plots. MATLAB program was employed to solve the equation with seven parameters.

cond-mat.mes-hall↗

arXiv2007

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.

cond-mat.mes-hall↗