Improvements of Magnetic Properties of Sm₂Fe₁₇C_x Melt-Spun Ribbons by Additional Elements

Before melt-spinning of the alloys, the formation of a Sm₂Fe₁₇ phase with Th₂Zn₁₇ type structure in Sm₂(Fe_0.9Cr_0.1)₁₇C_1.6 alloys is confirmed by studying the microstructure of ingots. Sm₂(Fe_0.9Cr_0.1)₁₇C_1.6 melt-spun ribbon exhibits the coercive force of 672 kAm^-1 (8.4 kOe) after annealing at 750°C for 30 min. Microstructural studies indicate that the ribbon consists of fine grains of 50–150 nm in diameter. It is found that a phase transformation from TbCu₇ to Th₂Zn₁₇ is caused with increasing annealing temperature, by X-ray analysis and the variation of magnetic hysteresis loops. The Ga containing ribbon of Sm₂(Fe_0.9Ga_0.1)₁₇C_1.6 exhibits the coercivity of 680 kAm^-1 (8.5 kOe) after annealing. A further addition of M (M=Co, Mn) to Sm₂(Fe, Cr₁₇)C_1.6 and Sm₂(Fe, Ga₁₇C_1.6) alloys improves the magnetic properties. Especially, (Sm₂Fe_0.85Ga_0.1Co_0.05)₁₇C_1.6 ribbon annealed at 650°C for 30 min exhibits high coercivity of 1008 kAm^-1 (12.6 kOe) with the (BH)max of 62.4 kJm^-3 (7.8 MGOe). This is the highest magnetic properties among the reported values of Sm₂Fe₁₇C_x melt-spun ribbons so far.