Influence of heat treatment on structure and reversal magnetization processes of Sm _12.5Co _66.5Fe ₈Cu ₁₃ alloy

In this work Sm _12.5Co _66.5Fe ₈Cu ₁₃ 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 SmCo ₅, Sm ₂Co ₁₇ and SmCo ₇ phases. Annealing at 850 °C for 3 h resulted in decomposition of the metastable SmCo ₇ phase into SmCo ₅ and Sm ₂Co ₁₇. 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.