Magnetic and structural properties of nano-sized Sm-FeCo-B particles

Nano-sized FeCo particles containing Sm and B are prepared by a co-precipit ation method. Each particle has a spherical shape with a diameter of about 20 mn and a core-shell structure. The core and shell mainly consist of the FeCo alloy and oxides containing Sm and B, respectively. The thickness of s urface layer is only about 1 run. The lattice spacing of the core part is e stimated to be 2.0 Angstrom which corresponds to that of (110) plane of bcc FeCo alloy. The saturation magnetization and the coercivity are 164 emu/g and 1420 Oe, respectively. The coercivity is larger than the calculated val ue (=500 Oe) for spherical single domain Fe particles.