Spin Reorientation, Magnetic Viscosity and Exchange Coupling Effects of the Nd-Ce-Fe-B Sintered Magnets Prepared by Singlemain-Phase and Dual-Main-Phase Alloy Methods

Temperature dependence of magnetic properties of 20%-Ce substitution Nd-Ce-Fe-B as-sintered and tempering magnets was investigated systematically. These magnets were fabricated by single-main-phase (SMP) and double-main-phase (DMP) methods, respectively. The DMP as-sintered magnet exhibits the highest M
_s
(~185emu/g) and M
_r
(~133 emu/g) among these specimens at 60K. Microstructural investigation shows that the component of DMP specimens varies in a large range; part of main phase is Ce-lean. Magnetic analysis indicates DMP tempering specimen has best temperature coefficient of remanent and coercivity over the measurement temperature range. The ac susceptibility investigation indicates the spin reorientation temperature increases from 80K for SMP specimens to 90K for DMP specimens, giving rise to the positive remanent temperature coefficient bellow 120K. The magnetic viscosity parameter of DMP as-sintered specimen is 4.23 emu/(g·s), the highest among the specimens, while DMP tempering specimen is only 2.07 emu/(g·s), indicating that tempering reduces magnetic viscosity of DMP specimens. The Henkle plots results indicate tempering reduce exchange coupling interaction between grains.