Investigations of magnetic and quadrupole properties of two-dimensional and square lattice spin-1 ising nanoparticle with dipole-quadrupole interactions

In this thesis, the magnetic (M) and quadrupole (Q) properties of two-dimensional and square lattice spin-1 Ising homogeneous and composite nanoparticle (NP) with bilinear (dipole-dipole / J), biquadratic (quadrupole-quadrupole / K), dipole-quadrupole (or odd / L) and crystal field (single-ion anisotropy / D) interactions have been investigated using the pair (bond) approximation. The bond energy parameters (ε_ij) for core (C), core-surface (CS) and surface (S) parts on square lattices were defined with the spin-1 Ising model. Using the bond energy, the self-consistent equations (P_ij) were solved to calculate the magnetization (M) and quadrupole (Q) order parameters. In this study, firstly, the results of the temperature dependence of magnetization and quadrupole order parameter for two-dimensional and square lattice spin-1 Ising homogeneous and composite nanoparticle are given. Magnetization and quadrupole order curves were examined in detail for different dipole-quadrupole interactions, radius and magnetic field values. Then, magnetic and quadrupole hysteresis curves for homogeneous and composite nanoparticles were obtained for different dipole-quadrupole interaction, temperature, and radius values. In particular, the effect of the L parameter on the hysteresis curves was also examined. In addition to these results, the variation of magnetization according to the crystal field was found for homogeneous and composite nanoparticles using different magnetic field and temperature values. By using different temperature, dipole-quadrupole interaction and crystal field parameters, the variation of the quadrupole value according to the magnetic field was calculated for homogeneous and composite nanoparticles. If we summarize the results obtained from the thesis study; It has been found that the dipole-quadrupole interaction value is also effective in addition to the bilinear, biquadratic, crystal field interactions of the new properties obtained in the investigation of the magnetic and quadrupole properties of two-dimensional and square lattice homogeneous and composite nanoparticles. The results were compared with other theoretical studies, and it was observed that they were compatible with the literature.