Magnetic structure and superconductivity in (HoxY1-x)Ni2B2C

The superconducting transition and the magnetic structure of polycrystalline (HoxY1-x)Ni2B2C have been investigated for x greater than or equal to 0.75 by resistivity measurements and neutron diffraction, respectively. For HoNi2B2C, the well known antiferromagnetic structure with c- and a-axis components existing between 4.5 and 6 K has been confirmed. Whereas for all investigated samples the component having the a-axis modulated structure exists in a narrow temperature range only, the intensity connected to the spiral magnetic state along the c-axis increases for x=0.85 and x=0.75 monotonically as the temperature decreases to the lowest measuring temperature of 1.6 K. Our results strongly suggest that the incommensurate modulated structure along the a-axis is responsible for pair breaking in the investigated (HoxY1-x)Ni2B2C samples. On the other hand, the magnetic spiral structure with c-axis wave vector was found to coexist with superconductivity. A linear suppression of the superconducting transition temperature with increasing Ho content was observed which is in agreement with the Abrikosov-Gor'kov theory. We found a linear scaling with the effective de Gennes factors (x DG) (He) for both the superconducting transition and the magnetic ordering temperatures. (C) 1997 American Institute of Physics.