Bulk anisotropic multiphase nanohybrid magnets fabricated from compound precursors

Abstract Bulk anisotropic RT 7 /α-Fe(Co)+Nd 2 Fe 14 B/α-Fe (RT 7 denotes Sm(CoFeCuZr) 7 phase) multiphase nanohybrid magnets have been designed and prepared by High-Pressure Thermal Compression (HPTC), using a blend of Nd 9 Fe 85.5 Cu 1.5 B 4 amorphous and SmCo-based amorphous-nanocrytalline powders as precursors. The resulting HPTC magnet is composed of alternating RT 7 /α-Fe(Co) and Nd 2 Fe 14 B/α-Fe nanocomposite layers along the pressure direction. A (00 l ) crystallographic texture for the RT 7 and Nd 2 Fe 14 B nanocrystals has been achieved in the RT 7 /α-Fe(Co) and Nd 2 Fe 14 B/α-Fe layers, respectively. The RT 7 /α-Fe(Co) layer comprises elongated RT 7 nanocrystals (8–13 nm in thickness and 13–20 nm in length) and approximately equiaxed α-Fe(Co) nanograins with an average size of ∼13 nm. The Nd 2 Fe 14 B/α-Fe layer consists of lath-shaped Nd 2 Fe 14 B nanograins (15–30 nm in thickness and 30–55 nm in length) and approximately equiaxed α-Fe nanograins with an average size of ∼19 nm. The HPTC magnet exhibits a maximum energy product of 25 MGOe, with a high soft-magnetic fraction of ∼30 wt%, and a low coercivity temperature coefficient of β (RT-250 °C)  = −0.28% o C −1 . Our work provides an alternative approach to yielding high-performance bulk multiphase nanohybrid magnets.