CRITICAL CURRENT DENSITIES IN MAGNETIC SUPERCONDUCTORS Dy1–xErxRh3,8Ru0,2B4 (x=0,2;0,4)

Rhodium borides of the compositions Dy0,8Er0,2Rh3,8Ru0,2B4 and Dy0,6Er0,4Rh3,8Ru0,2B4 were synthesized on the basis of the compound DyRh3,8Ru0,2B4 by partial substitution of dysprosium (Dy) with erbium (Er) with a LuRu4B4 type structure. The dependences of χ-1(T), M(B) and Bc2(T) were studied for these compounds. It is established that the compounds Dy0,8Er0,2Rh3,8Ru0,2B4 and Dy0,6Er0,4Rh3,8Ru0,2B4 are magnetic superconductors with a critical temperature Tc ≈ 5.1 and 5.8 K, respectively; at T ≈ 3 K the magnetic subsystem of these compounds goes into the antiferromagnetic state. Based on measurements of the magnetic moment from the field (M(B)) for samples of compounds Dy0,8Er0,2Rh3,8Ru0,2B4 and Dy0,6Er0,4Rh3,8Ru0,2B4, using the Bean model, dependences on the field of the critical current density jc(B) and the reduced pinning force fp(h) are obtained. The value of jc   in the studied samples did not exceed 400 A/cm2 at T ≈ 2 K. It is established that in the case of magnetic superconductors with antiferromagnetic ordering (Dy0,8Er0,2Rh3,8Ru0,2B4 and Dy0,6Er0,4Rh3,8Ru0,2B4) at h > 0.4 there is a significant deviation from the law of similarity.