Tuning Fe[sub.2]Ti Distribution to Enhance Extrinsic Magnetic Properties of SmFe[sub.12]-Based Magnets

The ThMn[sub.12]-type SmFe[sub.12]-based rare-earth permanent magnet has attracted widespread attention due to its excellent intrinsic magnetic properties and high-temperature stability. However, the challenge in realizing continuous non-magnetic or weakly magnetic grain boundary phases equilibrated with the SmFe[sub.12] main phase hinders the enhancement in extrinsic magnetic properties of the SmFe[sub.12]-based permanent magnet, especially for the coercivity. In this work, by controlling the cooling rate, the uniform distribution of paramagnetic Fe[sub.2]Ti phases at grain boundaries is achieved in the SmFe[sub.12]-based alloy ribbon, resulting in a high coercivity of 7.95 kOe. This improvement is attributed to the elimination of the impurity phase within the SmFe[sub.12] main phase and the magnetic isolation effect of the grain boundary phase composed of paramagnetic Fe[sub.2]Ti, which is directly observed by transmission electron microscopy and further confirmed by micromagnetic simulation. Moreover, first-principles calculations show that the V element can dope into Fe[sub.2]Ti and facilitate the transition of its paramagnetic state at room temperature. This study provides new insights into constructing weakly magnetic grain boundary phases for SmFe[sub.12]-based permanent magnets, offering a novel approach to enhance coercivity.