Microstructure of high coercivity FePt thin films fabricated at 400°C

FePt thin films with two structures are deposited on the (100) MgO substrate (FePt/MgO - Structure I; MgO/FePt/Ag/FePt/Ag/FePt - Structure II). With ultrathin Ag layers inserted between FePt layers, the out-of-plane coercivity of the film with Structure II increases to about 32.5 kOe at a deposition temperature of 400°C. The coercivity squareness S* (ΔH/H_c) is found to decrease from 0.66 in the film with Structure I to 0.38 in the film with Structure II. This suggests that the exchange coupling decreases with Ag intermediate layers inserted. Using AFM measurements, differences in the surface morphology of the two film structures are also studied.