Dynamic stress-induced low-temperature ordering of FePt

The ordering temperature of FePt was significantly reduced to 275degreesC by introducing a Cu underlayer on the HF-cleaned Si(001) substrate. A coercivity H-c as high as 6200 Oe can be achieved after postannealing at 275degreesC, and H-c can be further increased to 7000 Oe after 300degreesC postannealing. During the formation of copper silicide Cu3Si, the expanded volume induces a dynamic in-plane tensile stress on FePt films, which accelerates the formation of the ordered FePt phase at low temperature. Different from the static stress induced by the lattice mismatch between films and underlayers, the dynamic stress is relaxed after the formation of Cu3Si is completed; therefore, the low-temperature ordering of FePt mainly takes place simultaneously with the evolution of dynamic stress during the formation of Cu3Si. The coercivity of FePt depends on the amount of Cu3Si and on the stress developed by Cu3Si. (C) 2004 American Institute of Physics.