Arrangement effects of triangular defects on magnetization reversal process in a permalloy dot

►Introducing one triangular defect to the disk will induce the change of the intermediate state which depends on the direction of the defect. ►Chirality of the vortex state nucleated in the reversal process can be controlled by the triangular defect in the disk. ►Nucleation field of the vortex for the disk with a triangular defect is more sensitive than the cases of circular and square defects, and it is strongly dependent on the orientation of the triangular defect. ►Reversal mode for the disk depends on the arrangement of the triangular defects for the case of the disk including two triangular defects.