Microstructure and magnetic properties of anisotropic Nd–Fe–B thin films fabricated with different deposition rates

Abstract

Anisotropic Nd–Fe–B thin films with c-axis texture are fabricated by DC magnetron sputtering on heated Si substrates. The influences of deposition rate (DR) on the microstructure and magnetic properties of Nd–Fe–B thin films are investigated. It is found that the atomic ratio of Nd/Fe in Nd–Fe–B thin films is sensitive to DR, hence resulting in a change in magnetic properties. With increasing DR, the Nd/Fe atomic ratio increases monotonically. For the films sputtered at low DRs ( ⩽ 0.5 nm / s ), low coercivities are observed due to the existence of α-Fe or an absence of Nd-rich phase. Further increasing the DR ( ⩾ 0.6 nm / s ) results in a significant increase of coercivity up to 14.5 kOe, because the hard-magnetic Nd 2Fe 14B phase coexists with the Nd-rich phase in the films. Size of the surface grains increases with increasing DR, and for the films prepared at a high DR ( ⩾ 0.6 nm / s ), some island-like big grains appear on the film surface, which are correlated with the Nd-rich phase.