Magnetic structures and their influence on superconductivity in diluted rare earth nickel borocarbides

Complete text of publication follows. For series of superconducting HoxR1-xNi211B2C compounds with R Y, La and Lu, we investigated the fascinating interplay between magnetism and superconductivity. Inelastic neutron experiments on D1B and D2B at ILL, Grenoble and on E6 at HMI, Berlin, we found a commensurate c-axis modulated antiferromagnetic structure and two incommensurate magnetic structures, one c-axis modulated and one a-axis modulated. Correlated with changes in superconducting properties, the dilution by nonmagnetic Y [1], La [2] and Lu [3] affects strongly the volume fractions and evolution with temperature and concentration of all magnetic structures as well as the propagation vectors and the squaring-up-behavior of the incommensurate magnetic structures. The observed differences between Y, La and Lu in the modification of magnetic and superconducting properties can be explained by their different influence on the balance of RKKY-type interactions and crystalline electric field effects as well as on magnetoelastic and disorder effects. (author) [1] A. Kreyssig et al., Physica B 234-236 (1997) 737.; [2] J. Freudenberger et al., Physica C (1999), in print.; [3] A. Kreyssig et al., Physica B 241-243 (1998) 826