Evolution of magnetic order and loss of superconductivity m Er1-xTbxNi2B2C

Complete text of publication follows. The RNi2B2C (R = rare earth) family of superconductors enables the interplay between long range antiferromagnetism and superconductivity to be explored in considerable detail. The results of a powder neutron diffraction study of the evolution of magnetic order in the pseudoquaternary compounds formed by alloying superconducting ErNi2B2C (Tc = 10.5 K, TN = 6 K) with non-superconducting TbNi2B2C (TN = 15 K) are presented. It is well known that in the Er compound the rare earth moments are ordered in a spin density wave transversely polarised along the a-axis of the cell, whilst the spin density wave in the Tb compound is longitudinally polarised with respect to the a-axis. However our measurements show that although the component of the rare earth moment along the a-axis increases with increasing Tb concentration, this increase is not smooth, but instead is characterised by a marked step-wise change. This discontinuity occurs between 0.25 < x < 0.30, coincident with the loss of superconductivity. This result is discussed in the context of the detailed structural and magnetic phase diagram extracted from profile refinement of our powder diffraction spectra. (author)