Effects of silicon composition on glass formation, crystallization behavior, phase evolution and magnetic properties of the melt-spun Mn-Si-B ribbons

Abstract

The glass formation, crystallization behavior, phase precipitation, and magnetic properties for a series of melt-spun Mn93−xSixB7 (x = 15, 20, 25, 30) amorphous ribbons were investigated. For x = 15 and 20 amorphous alloys, the crystallization shows one-stage behavior but different precipitated phases. For x = 25 amorphous alloy, a two-stage crystallization behavior occurs, in which the first and second crystallized peaks precipitate the Mn5Si3 and Mn2B, respectively. The broad maximum peak emerges at the temperature-dependent magnetization M(T) curves, indicating the amorphous alloys' spin glass (SG) behavior. Furthermore, the nanocrystalline and amorphous composite structure (NACS) consisting of the single nanocrystalline Mn5Si3 and amorphous phase can be achieved for the amorphous Mn93−xSixB7 alloy with x = 25 by controlling the annealing temperature and duration. The magnetic transitions of the NACS sample significantly differ from the counterpart of its amorphous state. The amorphous alloy undergoes the magnetic phase transition from SG into a paramagnetic state at about 20 K. In comparison, the annealed NACS sample first transforms the SG into a ferromagnetic state at about 15 K and then into a paramagnetic state around 300 K. The difference could attribute to the coupling effect between the nanocrystalline Mn5Si3 with the amorphous phase.