Hysteretic response characteristics of the ising-type nanomagnetic materials

The conceptual frame of the surface enhancement phenomenon on finite magnetic materials, especially on thin-films and semi-finite systems, has not lost its currency yet and recently there has been growing interest for this mature subject of solid state physics because a variety of apparently very different phenomena can be described by both experimentalists and theorists. This thesis deals with the hysteretic features of Ising-type thin films under external oscillatory magnetic field. Throughout the analysis, the most appropriate parameter values are chosen since they would allow us to observe the reversed magnetic hysteresis after a certain value of external field frequency. This eccentric phenomenon has prompted us to associate it to the domain nucleation and growth mechanism. The exotic shapes of the response in two different regimes of modified surface exchange are particulary emphasized. The results are essentially based on two related papers of us including aforementioned systems: By means of effective field theory (EFT), dynamical phase diagrams of Ising-typed pure crystalline thin-films with different thicknesses have been presented. An attempt is made to explain the relations between the competing time scales (intrinsic microscopic relaxation time of the system and the time period of the external oscillatory field) and frequency dispersion of the critical temperature coordinate of the special point. In order to elucidate the nature of hysteresis characteristics in a magnetic Ising-type thin film with a certain thickness, such as types of frequency dispersion curves, corresponding coercive field and remanent magnetization values, etc. have also been propounded in other complementary work.