Hossein Raanaei

In this research work, the magnetic behavior of a series of elliptical ferromagnetic nanodots including defect have been investigated by using micromagnetic simulation performed with OOMMF software. The magnetic hysteresis loops, magnetic patterns and magnetization reversal are examined. Two position cases of the ellipses are verified where the external magnetic field is parallel and perpendicular to the major (easy) axes. Different aspect ratio (minor axes/major axes) of elliptical nanodots are considered. The defect position is altered and specified from the origin of the dots. The magnetic transitions often occur when the C state surrounding the defect position. The more durability of the magnetic transition is accompanied by the more switching fields numbers. In the case of parallel field, with increasing the defect position, the coercivity fields decrease. It is observed that the calculated coercivity field when the field is perpendicular is often greater than that the case, field is parallel. Both exchange and demagnetization energy are employed to describe the magnetic characterization of the dots. In the case of perpendicular field, with increasing the defect position, a considerable deference of the maximum exchange values between the lower and higher aspect ratio of the elliptical dots is observed; Moreover in such a case, for all the magnetic dots, the switching field values are vividly altered once the defect is moved to the point positioning at the distance 1/8 of the major axis from the ellipses center