Accumulating evidence for the two-step magnetic ordering in the borocarbides DyNi2B2C and DyCo2B2C

Abstract Accumulating evidence for a two-step magnetic ordering in the borocarbide DyNi2B2C is summarized, including earlier overlooked evidence for the initial magnetic transition and a recent magnetization study of polycrystalline samples. The two-step ordering involves initial two-dimensional ferromagnetic ordering in the DyC (basal) planes at TN (=16.3 K), gradual build-up of the three-dimensional (3D) alternate stacking of ferromagnetic planes, and a final 3D ordering in the AF–I-related structure at a lower temperature To (=10.4 K), depicting a first-order transition. Supporting evidence for the two-step magnetic ordering in DyNi2B2C comes from point-contact spectroscopy measurements in the normal state for DyNi2B2C–Ag contact, and from similar behaviour of PrNi2B2C and (Pr0.91Dy0.09)Ni2B2C. In the isostructural borocarbide DyCo2B2C the two magnetic transitions (at 7.8 and 2.6 K) deduced from the specific-heat measurements are also attributed to a two-step magnetic ordering.