Structure and magnetic properties of SmCo7−xGax (0⩽x⩽1.2) alloys

Abstract

• Effects of Ga addition on structure and magnetic properties of SmCo 7 alloy were studied. • A stable TbCu 7 -type single phase can be obtained in as-cast SmCo 6.1 Ga 0.9 alloys. • Ga addition affects the stability, order degree and nucleation of 1:7H phase. • TbCu 7 -type phase in the ribbons is basically stable below 500 °C. • The phase transition of ribbons during the heating process was discussed. In this article, the effects of Ga addition on the structure and magnetic properties of SmCo 7 alloy were studied. The results show that a stable TbCu 7 -type single phase can be obtained in as-cast SmCo 7− x Ga x alloys when a proper amount of Ga is introduced ( x = 0.9). Meanwhile, all SmCo 7− x Ga x ribbons melt-spun at 40 m/s are composed of single TbCu 7 -type phase. So both the appropriate doping of Ga, and more especially the rapid cooling rate, can effectively stabilize the TbCu 7 -type structure. Moreover, Ga addition affects not only the stability and the order degree of 1:7H phase but also the uniformity of nucleation. Magnetic tests reveal that the coercivity, remanence and remanence ratio of the ribbons increase with the Ga addition, and reach their maximum values (7117.0 ± 2081.5 Oe, 36.7 ± 4.2 emu/g and 0.771 ± 0.037, respectively) when x = 0.9. At the same time, the maximum magnetization of ribbons and Curie temperature ( T c ) of Sm–Co phases tend to decrease with the amount of Ga. In particular, the TbCu 7 -type phase in SmCo 7− x Ga x ribbons is basically stable below 500 °C, and the phase transition during the heating process is also discussed.