Magnetic Properties and Microstructures of Sm–Fe–Ti Alloys With ThMn12 Structure Prepared by Melt-Spinning Method

The effects of annealing temperature ( $T_{a}$ , 600 °C–950 °C) and Sm content on the phase transformation and magnetic properties of Sm _x Fe ₁₁ Ti ( $x $ = 0.9, 1.0, and 1.1) alloys prepared by the melt-spinning method were investigated. In all specimens with different compositions, the crystal structure was transformed from the TbCu ₇ to ThMn ₁₂ structure as $T_{a}$ increased. The coercivity reached 6.3 kOe in a SmFe ₁₁ Ti ribbon annealed at 850 °C. However, the grain size of this ribbon was much smaller than the critical single domain size of the SmFe ₁₁ Ti alloy. The microstructural analysis revealed that the ribbons were highly strained. To overcome the abnormal low coercivity of SmFe ₁₁ Ti alloy, precise control of the composition and removal of strain without grain growth are the critical factors.