Magnetic properties of Sm_1Fe_7N_δ isotropic bulk magnets fabricated by high-pressure current sintering

摘要

Isotropic Sm_1Fe_7N_δ sintered magnets were fabricated from coarse powder with flake form by a high-pressure current sintering. The obtained magnets had a high density of ~92% without thermal decomposition. Thus, these magnets perfectly maintained coercivity of the raw powder, resulting in a high (BH)_(max) of 17 MGOe. Magnetic characterization under hot environment clarified their small temperature coefficients of H_(cj), -0.59 %/°C. In addition, aging tests with different temperature demonstrated that flux density of the sintered compacts did not largely decrease with an increasing in temperature unlike Nd-Fe-B magnets. As a result, even though the Sm-Fe-N sintered magnets were isotropic magnets, they exhibited comparable flux density to Nd-Fe-B anisotropic magnets above 200°C.