Magnetic properties and grain-boundary structure transition of melt-spun (Sm0.12Co0.87Cu0.01)97(VC)3 under annealing

Abstract Effects of annealing treatment on the magnetic properties and microstructure of SmCo 7 -based magnets doped with VC and Cu were investigated. The coercivity of the as-spun ribbons (Sm 0.12 Co 0.87 Cu 0.01 ) 97 (VC) 3 was 3.6 kOe. It was increased to 7.3 kOe after annealing at 800 °C for 15 min. A fixed single 1:7H structure and regular 1:7H dendrite grains with long axes preferentially parallel to each other had been attained during rapid solidification and subsequent annealing treatment. However, TEM results revealed that there was grain-boundary phase rich in C and Cu besides 1:7H phase in the as-solidified ribbon. After annealing, the grain-boundary phase decomposed to Cu-, Sm- and C-rich intergranular phases. Cu-, Sm- and C-rich regions formed at the grain boundaries after annealing improved the coercivity of (Sm 0.12 Co 0.87 Cu 0.01 ) 97 (VC) 3 by decreasing the magnetostatic interactions and act as effective domain wall pinning sites.