Excellent magnetic properties determined by spinodal decomposition structure of Alnico alloy doped SmCo5-based ribbons

5 wt% Alnico5 doped Sm(Co_0.9Cu_0.1)₅ ribbons were prepared by melt spinning at 40 m/s, and the effects of magnetic field heat treatment (MHT) and annealing on the phase composition, microstructure and magnetic properties of the ribbons were investigated. The results show that all three ribbons consist of Co-rich SmCo₅-and Sm-rich CeCo₅-type phases with a spinodal structure. Annealing increases the content of SmCo₅-type phase, enlarges the component differences between the two types of Sm(Co,M)₅ phases and accumulates Alnico alloying elements into 3 g site of CeCo₅-type phase. MHT narrows the ingredient differences between them, prompting the Alnico alloying elements to diffuse simultaneously into 2c and 3 g sites of two Sm(Co,M)₅ phases, and concentrates the CeCo₅-type phase on grain boundaries of the SmCo₅-type phase to pin the magnetic domain movement. The as-spun ribbons present the magnetic properties of H_c = 32.0 kOe, M_r = 46.2 emu/g and M_s = 59.1 emu/g, while MHT increases them by 10.0%, 10.2% and 19.5%, respectively. These results can contribute to disclose the multi-element doping mechanism for improving the magnetic properties of SmCo₅-based or similar alloys.