Structural and Magnetic Properties of Sm(CobalFe0.1Ni0.12Zr0.04B0.04)7.5 Melt Spun Ribbons

Abstract

We have investigated the structural and magnetic properties of Sm(Co0.70Fe0.1Ni0.12Zr0.04B0.04)7.5 melt spun ribbons. The arc-melted bulk samples have been used to obtain ribbons at 37 up to 55 m/sec while annealing has been performed in argon atmosphere for 30-75 min at 600-870 oC. In as-spun ribbons the hexagonal SmCo7 (TbCu7-type of structure) of crystal structure has been determined from x-ray diffraction patterns, while fcc-Co has been identified as a secondary phase. After annealing, the 1:7 phase of the as-spun ribbons transforms into 2:17 and 1:5 phases. TEM analysis shows a homogeneous nanocrystalline microstructure with average grain size of 30-80 nm. Coercivity values of 15-27 kOe are obtained from hysteresis loops traced at non-saturating fields. The coercivity decreases as temperature increases, but it is high enough to maintain values higher than 5 kOe at 380 oC. The maximum energy product at room temperature increases, as high as 7.2 MGOe, for melt-spun ribbons produced at higher wheel speed.