OCCURRENCE AND COMPOSITION DEPENDENCE OF SUPERCONDUCTIVITY AND MAGNETISM IN HONI2B2C

The dependence of the superconducting and magnetic properties of the re-entrant superconductor HoNi2B2C on phase composition was investigated with X-ray powder diffractometry, AC susceptibility measurements at ambient and applied pressure, and resistivity measurements. The experimental results based on over 40 polycrystalline samples show that this phase occurs with three different types of behaviour: pure superconductivity, re-entrant behaviour and a non-superconducting state. Starting from a pure superconducting state, with changing phase composition anomalies develop around 5.5 K and 6 K in the AC susceptibility, followed by re-entrant superconductivity. The anomalies are attributed to the manifestation of modulated magnetic states, which are destructive to superconductivity. The application of hydrostatic pressure results in a modification of these anomalies. Further composition change leads to a complete loss of superconductivity. The influence of volume contraction and substitution effects will be discussed.