Structural, microstructural and magnetic properties of nanocomposite isotropic Sm(CobalFe0.1MyZr0.04B0.04)7.5 ribbons with M=Ni, Cu and y=0.09 and 0.12

Abstract In boron-substituted melt-spun Sm(Co,Fe,Cu,Zr) 7.5 -type alloys a nanocomposite microstructure and high coercivities in both as-spun and short-time annealed ribbons can be obtained. In the present study three different compositions, namely Sm(Co 0.73 Fe 0.1 Cu 0.09 Zr 0.04 B 0.04 ) 7.5 , Sm(Co 0.70 Fe 0.1 Cu 0.12 Zr 0.04 B 0.04 ) 7.5 and Sm(Co 0.70 Fe 0.1 Ni 0.12 Zr 0.04 B 0.04 ) 7.5 have been examined in order to investigate the influence of composition on the magnetic properties and the microstructure. Melt-spun ribbons have been obtained and annealing has been followed under argon atmosphere for 30–75 min at 600–870 °C. For the as-spun ribbons the TbCu 7 -type of structure and fcc-Co as a secondary phase have been identified in the X-ray diffraction patterns. For the annealed ribbons above 700 °C the 1:7 phase transforms into 2:17 and 1:5 phases. The TEM studies have shown a homogeneous nanocrystalline microstructure with average grain size of 30–80 nm. Coercivity values of 15–27 kOe have been obtained from hysteresis loops traced in non-saturating fields. The coercivity decreases with temperature, but it is sufficiently large to maintain values higher than 5 kOe at 380 °C.