Abstract
The temperature dependence of magnetic ordering and the superconducting transition have been studied for polycrystalline Ho x Lu 1− x Ni 2B 2C compounds by susceptibility and resistivity measurements as well as neutron diffraction. For Ho concentrations in the range 0⩽ x⩽0.7, the superconducting transition temperature, T c, decreases from 16.5 K at x=0 linearly with increasing x and, consequently, with increasing effective de Gennes factor. This is in accordance with a generalized Abrikosov–Gor'kov theory. At x=0.7, T c reaches 8.5 K i.e. the value of HoNi 2B 2C. Pair breaking by the Ho magnetic moments is stronger in Ho x Lu 1− x Ni 2B 2C compared to Ho x Y 1− x Ni 2B 2C. This is attributed to the difference between the lattice constants of the Ho–Y and the Ho–Lu systems resulting in different electronic structure parameters. A complete breakdown of the scaling behaviour of T c occurs for x>0.7, where T c becomes independent of the effective de Gennes factor. In this range of x re-entrant behaviour and the presence of an incommensurate a-axis, modulated antiferromagnetic structures have been observed below a characteristic temperature T m. Commensurate and incommensurate c-axis modulated antiferromagnetic structures that are observed both in the Ho–Y and the Ho–Lu systems coexist with superconductivity.
Published Version
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