Magnetic Domain Structures and Magnetic Properties of Lightly Nd-Doped Sm-Co Magnets With High Squareness and High Heat Resistance

The relationship between magnetic domain structures and magnetic properties of Nd-doped Sm(Fe, Cu, Zr, Co) 7.5 was investigated. In the preparation process, slow cooling between sintering and solution treatment was employed to promote homogenization of microstructures. The developed magnet achieved a maximum energy product, [ BH ] m , of 33.8 MGOe and coercivity, {H} _{\mathrm {cb}} , of 11.2 kOe at 25 °C, respectively. Moreover, {B} - {H} line at 150 °C was linear, which means that irreversible demagnetization does not occur even at 150 °C. Temperature coefficients of remanent magnetic flux density, {B} _{r} , and intrinsic coercivity, {H} _{\mathrm {cj}} , were 0.035%/K and 0.24%/K, respectively, as usual the conventional Sm-Co magnet. Magnetic domain structures were observed with a Kerr effect microscope with a magnetic field applied from 0 to −20 kOe, and then reverse magnetic domains were generated evenly from grain boundaries. Microstructures referred to as "cell structures" were observed with a scanning transmission electron microscope. Fe and Cu were separated to 2-17 and 1-5 phases, respectively. Moreover, without producing impurity phases, Nd showed the same composition behavior with Sm in a cell structure.