Hard magnetic properties and microstructure of melt-spun Sm2Fe15-xCuxGa2C (x = 0 and 0.5) ribbons

The structure, magnetic properties and microstructure of Sm2Fe15-xCuxGa2C (x = 0 and 0.5) ribbons prepared by melt spinning and subsequent heat treatment were studied. A significant increase in coercivity has been found for ribbons prepared with the addition of a small amount of Cu. The maximum coercivity mu(0)H(c) is 1.4 and 2.0 T at room temperature for ribbons with x = 0 and 0.5, respectively, after annealing in vacuum at 1043 K for 15 min. A small amount of Cu addition has little effect on the lattice parameters, Curie temperature T-C, and magnetocrystalline anisotropy field H-A at room temperature, while it decreases the saturation magnetization M-s . The magnetocrystalline anisotropy constants K-1 and K-2 for the x = 0 and 0.5 samples were determined in the temperature range between 50 and 293 K, using magnetically aligned samples. The variations of coercivity, magnetization, and remanence as functions of applied field and temperature are consistent with the view that the magnetization of Sm2Fe15-xCuxGa2C ribbons with x = 0 as well as 0.5 are mainly controlled by pinning of domain walls. High- resolution transmission electron microscopy and energy-dispersive x-ray analysis demonstrate that Cu atoms dissolve partially into the 2:17-type matrix phase in Sm2Fe14.5Cu0.5Ga2C ribbons, which is effective in pinning the domain walls and enhancing the coercivity. (C) 1999 American Institute of Physics. [S0021-8979(99)01405-X].