Competition between Ferromagnetism and Superconductivity in HoMo6S8

Neutron scattering has been used to investigate the development of magnetic order in the region of the reentrant superconducting transition in Ho${\mathrm{Mo}}_6$ ${\mathrm{S}}_8$. On cooling, an ordered oscillatory magnetic state develops in the superconducting phase, with a wavelength which increases with the application of a magnetic field. On further cooling the sample reverts to the normal conducting state as ferromagnetism sets in. No oscillatory magnetic phase is observed, however, when the superconducting phase is approached from low temperatures.