Unusually large coercive field in Sm–Ru–B–C system

In our studies of the quaternary system Sm-Ru-B-C, samples of nominal composition Sm(1)Ru(2)B(2)C(1) and Sm(1)Ru(3)B(3)C(1) gave materials of essentially single phase with a hexagonal structure (a = 5.551 A, c = 2.976 A and a = 5.569 A, c = 2.955 A, respectively). The X-ray diffraction patterns resemble that of hexagonal SmRu 3 B 2 (a = 5.536 A and c = 2.997 A). We suggest that in SmRu 3 B 2 carbon may be partially substituting B or occupy interstitial sites giving materials of the type SmRu 3 B x C y . The two materials order ferromagnetically with T c ∼ 60 K and ∼ 50 K, respectively. At 5 K, they show magnetic hysteresis with a very large coercive field, H c ∼ 15 T. This is perhaps the largest He at 5 K for a Sm-based material.