Study On Preparation Technology And Properties Of Nd / NdFeB / α-Fe Multilayer Composite Films

NdFeB permanent magnetic material has wide application value as the core represents in rare-earth permanent magnetic material. Its application is developing to micro aspect. At present, the maximum energy product of NdFeB alloy has reached 56.10 MGOe. However, the maximum energy product of thin films still has a big gap with its theoretical value. Therefore, it has important theoretical and practical significance to study systematically the NdFeB permanent magnetic thin film.In this paper, Mo/[NdFeB/α-Fe]n/Mo thin films were prepared by magnetron sputtering, Mo/Nd/NdFeB[NdFeB/α-Fe]n/NdFeB/Nd/Mo thin films were also prepared by magnetron sputtering. The surface morphology of thin films was determined by the atomic force microscope, the phase structrue of thin films were analysized by the X-ray powder diffractometer, the cross-section growth condition of thin films were observed through the scanning electron microscope. The magnetic properties of thin films were measured on LDJ9600 Vibrating Sample Magnetometer.Mo/[NdFeB/α-Fe]n/Mo sputtered thin films were annealed at 630℃ for 30 min. The research results show that exchange coupling effect of soft and hard magnetic phase occurred well in two-phase thin films and remanence enhancement effect is obvious. Although there are a lot of α-Fe phase in the thin films,the thin films still show a single-phase hard magnetic behavior. However, the number of peak phase of Nd2Fe14 B in thin films phase structure is small and the strength of the peak is very weak.Thus, the coercivity of thin films is very low. When α-Fe layer thickness is 30 nm, magnetic properties of the thin film is the best.Mo/Nd/NdFeB[NdFeB/α-Fe]n/NdFeB/Nd/Mo thin films were annealed at 630℃ for 30 min. There are a lot of peaks phase of Nd2Fe14 B in thin films phase structure, indicating that Nd layer diffusion into NdFeB layers result in more Nd2Fe14 B phase in thin films than single NdFeB thin films. Therefore, the magnetic properties of thin films has also been greatly improved compared with the single thin film. With the thickness of α-Fe layer increases, the coercivity of thin films decreases, but the remanence and maximum energy of thin films increases. Without α-Fe layer, the parallel and perpendicular coercivity of the thin films were 14.5kOe and 10.5kOe, respectively; the parallel and perpendicular remanence of the thin films are 7.31 kGs and 5.23 kGs, respectively; the parallel and perpendicular maximum energy of the thin films were 11.5MGOe and 2.4MGOe, respectively. When the thickness α-Fe layer is 8nm, the parallel and perpendicular coercivity of the thin films were 6.01 k Oe and 6.96 kOe, respectively; the parallel and perpendicular remanence of the thin films were 16.64 kGs and 8.21 kGs, respectively; the parallel and perpendicular maximum energy of the thin films were 15.51 MGOe and 4.67 MGOe, respectively.