The L1(0) FePt (10 nm)/Fe (delta nm, delta = 0-15) bilayers were fabricated by using magnetron co-sputtering. The L1(0) FePt single layer shows good perpendicular orientation and the in-plane hysteresis loop shows almost a linear behavior. When delta is less than 3 nm, the FePt/Fe bilayers show behaviors like one magnetic phase, the coercivities are close to the values determined by Zeeman energy. When delta is larger than 3 nm, the in-plane hysteresis loops show behaviors similar to a soft magnetic film, the coercivities of the bilayers decreases slowly with the increasing Fe thickness because of confining by the exchange length of FePt layer and Fe layer. The measured coercivities values are optimally fitted by a 1/t(Fe)(1.15) relation. The magnetization reversal process and magnetic interaction were also investigated. (C) 2012 Elsevier B.V. All rights reserved.