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Exchange-coupled PtFe/Fe composite films have been prepared with Si3N4 as spacer layer and buffer layer. The coercivity generally decreases with increasing thickness of the Fe layer at fixed thickness of the Si3N4 spacer layer. At fixed thickness of Fe the layer, the coercivity shows a maximum and then declines with increasing thickness of the Si3N4 spacer layer because Si3N4 layer is too thin to play a role of separation. However, the magnetic properties are significantly enhanced by a Si3N4 buffer layer, which is proposed to be due to effective prevention of diffusion between Mo and PtFe phase, as indicated by microstructure images. Fine grain sizes estimated to be about 30 nm, an enhanced coercivity and better remanence ratio indicate the beneficial effects of Si3N4 buffer layer on the magnetic properties and on the exchange-coupling of PtFe/Fe composite films. [ABSTRACT FROM AUTHOR]