Nucleation-type magnetization behavior in FePt (001) particulate films

Nucleation-type magnetization behavior is reported in sputtered FePt (001) films with an island structure, where the particles show a multiple-domain structure. A large coercivity H _C of more than 50 kOe is achieved at an initial applied field of only 6 kOe. The magnetization behavior and the magnetic domain observation indicate clearly that domain walls are wiped out completely at a low applied field, and once domain walls are wiped out, it is hard to nucleate reversed domains in the particles, resulting in high H _C. The remarkable nucleation-type behavior of magnetization is also found to give rise to anomalous minor loops when the applied magnetic field is alternated around zero and increased gradually.