Beneficial Effects of ${\rm Si}_{3}{\rm N}_{4}$ Buffer/Spacer Layers on the Magnetic Properties of Exchange-Coupled PtFe/Fe Composite Films

Exchange-coupled PtFe/Fe composite films have been prepared with Si
₃
N
₄
as spacer layer and buffer layer. The coercivity generally decreases with increasing thickness of the Fe layer at fixed thickness of the Si
₃
N
₄
spacer layer. At fixed thickness of Fe the layer, the coercivity shows a maximum and then declines with increasing thickness of the Si
₃
N
₄
spacer layer because Si
₃
N
₄
layer is too thin to play a role of separation. However, the magnetic properties are significantly enhanced by a Si
₃
N
₄
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 Si
₃
N
₄
buffer layer on the magnetic properties and on the exchange-coupling of PtFe/Fe composite films.