Annealing dependence of magnetic properties in nanostructured Sm0.5Y0.5Co5

Nanocrystalline Sm0.5Y0.5Co5 powders with high coercivity HC and enhanced remanence Mr were prepared by mechanical milling and subsequent annealing. Annealing temperatures T ranging from 973 to 1173 K, and times t ranging from 1 to 5 min were used. X-ray diffraction (XRD) and DC-magnetization measurements were carried out to study the microstructure and magnetic properties of these samples. XRD patterns demonstrate that the average grain size 〈D〉 of the nanocrystalline powders depends on the annealing temperature T and time t: 〈D〉 ranges from 11 nm (for T=973 K and t=1 min) to 93 nm (for T=1173 K and t=5 min). Magnetic measurements performed at room temperature indicate high coercivity values (HC>955 kA/m), and enhanced remanence (Mr/Mmax>0.5) for all samples. A strong annealing-induced grain size dependence of these magnetic properties was found.