Phenomenological analysis of magnetization reversal process for L10-FePt(001) particulate films

The magnetization reversal processes for L1(0)-FePt(001) particulate films before and after Ar ion irradiation were experimentally investigated, and the size of the defect region (2r(0)) and the effective demagnetization factor (N-eff) were evaluated based on a phenomenological analysis. A large coercivity (H-c) of 30.4 kOe, which originates from the particulate structure, drastically reduced after ion irradiation. The phenomenological analysis showed the increase of 2r(0) by irradiating Ar ions, which clearly indicates that H-c is closely related with the size of 2r(0). In addition, the FePt particulate films show large Neff, which may arise from the large dipole interaction between particles and the distribution of particle sizes and shapes. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3058615]