Magnetic and structural properties of melt-spun rare-earth transition-metal intermetallics with ThMn12 structure

The magnetic and structural properties of melt-spun R8Fe84Ti8 with R=Nd, Sm, Dy, Gd and R8(Fe,Co)76[V(Mo)]16 with R=Nd, Sm have been studied with x-ray diffraction, transmission electron microscopy, and magnetic measurements. The tetragonal ThMn12-type structure was found in all alloys after annealing at about 700 °C. The Curie temperature (Tc) of the as-spun amorphous samples was in the range of 40–100 °C. Crystallized Nd8(Fe1−xCox)84Ti8 samples with the 1:12 structure have a Tc around 250 °C for x=0, reaching the value of 660 °C for x=0.5 and then decreasing again to 490 °C for x=1. ac susceptibility studies on Co-substituted samples showed magnetic transitions in the temperature range 100–200 K. The coercivity was found to be strongly dependent on the microstructure. The highest value of Hc (2 kOe) was obtained in Sm-Fe-Ti samples with a grain size about 500 Å. The upper value of Hc is low because of the presence of some α-Fe in crystallized ribbons.