The mechanism of enhanced coercivity for (CeNdPr)-Fe-B sintered magnet prepared by structure design

Because of the high saturation magnetization (μ₀M_s=1.6 T) and high magnetocrystalline anisotropy (K_u=4.5 MJ/m³) of the Nd₂Fe₁₄B phase, anisotropic Nd-Fe-B sintered magnets exhibit the highest energy product (474 kJ/m) of all the permanent magnetic materials. However, the issue on substitution of Pr-Nd or Nd by Ce attracted renewed attention, due to the cost pressure of Nd, PrNd alloy and the large quantity of Ce metal. Traditional sintered method and the die-upset or hot-press process have been devoted to magnetic hardening of (CePrNd)-Fe-B magnets. These experiments indicated that the magnetic properties of the as-prepared magnets greatly decreased due to the low saturation magnetization and the poor anisotropy field of the Ce₂Fe₁₄B. To obtain the excellent magnetic properties for the Ce substitution magnets, we proposed a double main phase method to prepare the high permanence (CePrNd)-Fe-B magnet with low cost. The schemes of the magnet prepared by traditional sintered method and the double main phase method are shown figure 1. It is obviously that, compared to the traditional sintered method adjusting the composition of the magnet, the double main phase method also can design the distribution of the main phase in the magnet, which makes the structure satisfy the demand of the magnet with outstanding properties. In this work, the double main phase magnet AB and the single alloy magnet C were prepared. The extrinsic magnetic properties of the as-prepared samples AB and C were measured by vibrating sample magnetometer at room temperature with the maximum field of 30 kOe.