Nanocomposite Nd-Fe-B / α-Fe thin films were prepared by sputtering successively a Nd-rich Nd21Fe64B15 and a Fe targets in a multilayer structure using radio frequency (RF) magnetron gun. We have studied the influence of thickness of α-Fe layer on the magnetic properties of Nd-Fe-B / α-Fe thin films. A nanocomposite thin film with 15nm thick α-Fe layer prepared on 550°C heated substrate gives the highest energy product, 190 kJ/m3 along with a coercivity of 950 kA/m. Magnetic hysteresis loop measurement shows that the hard (Nd-Fe-B) and soft (α-Fe) layers are exchange coupled firmly for the films deposited on heated substrate whereas the two layers are decoupled for room temperature deposited and post annealed films. © 2010 IOP Publishing Ltd.