The susceptibility spectra originating from both relaxation processes of reversible domain wall motion and magnetization rotation are decomposed from the susceptibility spectrum for 3% SiFe samples implanted by N-ion in the fluence range of n=5×10 −5–5×10 18 ions/cm 2. The static susceptibilities due to domain wall motion and magnetization rotation are maximum at n=5×10 17 ions/cm 2. The relaxation frequencies of domain wall motion and magnetization rotation are not changed significantly up to n=5×10 17 ions/cm 2, and then rapidly increased with the further increase in the ion fluence. The variation of static susceptibilities and relaxation frequencies with n indicate that increase in number of pinning sites for n⩽5×10 17 ions/cm 2 to facilitate magnetization, and then increase in internal stress for n>5×10 17 ions/cm 2 to hinder magnetization.