Influence of heat treatment on structure and reversal magnetization processes of Sm12.5Co66.5Fe8Cu13 alloy

In this work Sm12.5Co66.5Fe8Cu13 ribbons, in the as-cast state and after annealing at 850 °C for 3 h, were studied. The investigated samples were obtained using the melt-spinning method. On the basis of X-ray diffraction patterns, it was found that sample in the as-cast state consisted of 0.88%, 14.47% and 84.65%, respectively of SmCo5, Sm2Co17 and SmCo7 phases. Annealing at 850 °C for 3 h resulted in decomposition of the metastable SmCo7 phase into SmCo5 and Sm2Co17. The magnetic measurements were performed using VSM, working in a magnetic field up to 2 T. From the hysteresis loops the magnetic parameters were determined. It was found that annealing process leads to deterioration of remanence from 0.60 T to 0.44 T and large increase in the coercivity from 1 kOe to 3.6 kOe. From the analysis of the recoil loops, it was found that the reversal magnetization process is complicated and mainly based on pinning of domain walls on grain boundaries.

► Investigated melt-spun as-cast state ribbons had multiphase structure, mainly composed of SmCo7 phase.
► Annealing resulted in decomposition of the metastable SmCo7 phase into SmCo5 and Sm2Co17. That resulted in improvement of hard magnetic properties.
► From the recoil loops it was found that the reversal magnetization process is complicated, mainly based on pining of domain walls on grain boundaries but also supported by nucleation processes.