We have studied the effect of Ta on the structure, magnetic properties and the ordering temperature of FePt(Ta) thin films. The samples are prepared by the dc and rf magnetron cosputtering method with 3 single element targets. After a deposition, the samples are annealed in a vacuum at various temperatures. The XRD patterns show strong (111) peaks at all annealing temperatures, but the change in the d-spacings reveals a disorder-order transformation. The more Ta is added to the FePt, the larger the coercivity becomes. The coercivity of the FePtTa40W film annealed at 700°C reaches about two times as large as the value of the pure FePt film. The delta m curves imply that Ta atoms diffuse into the grain boundary to reduce inter-granular exchange coupling, which leads the enhancement of coercivity.
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