Tremendous enhancement of magnetic performance for Sm(CoFeCuZr)z magnet based on multiscale copper redistribution

Abstract Microstructure and magnetic properties were studied for the commercial Sm(CoFeCuZr)z magnets before and after post annealing treatment. The results show that the phases composition and orientation of the magnet do not change after post annealing treatment, but the substantial redistribution of Cu element within multiscale (the microscale crystal grain and the nanoscale cellular structure) had been observed simultaneously. In detail, as the Cu redistribution, the thickness of the Cu-rich Sm(Co,Cu)5 cell boundary becomes thinner, and the Cu concentration in the boundary increases sharply. The pinning field of domain walls and corresponding coercivity increases remarkably with slight remanence and maximum energy product loss, and the overall magnetic performance of (BH)max (MGOe)+Hcj (kOe) increases by 54.3% as a result. Moreover, the thermal stability of the magnet improves as well. On the other hand, Cu-lean phenomenon was observed along the grain boundary region, triggering to magnetic domain reversal process and slightly undermining the squareness of the demagnetization curve of the magnet.