A neutron scattering study of the coexistence of magnetism and superconductivity in HoMo6S8 single crystals

Abstract From neutron scattering experiments, using a HoMo 6 S 8 single crystal and measuring simultaneously the resistivity, we have established: 1. i) Below T m1 =0.75 K, the first order magnetic transition at T m2 =0.70 K, between the long range transverse sine wave modulated ordering ( λ=570 A ) and the transverse antiphase modulated phase ( λ=1700 A ), is distinct from the second order superconducting transition T c2 =0.685 K at which the zero resistance disappears. Actually this transition occurs when Ho 3+ moments reach a value yielding a critical magnetic induction B c2 =3170 G. 2. ii) Below T c2 , HoMo 6 S 8 does not reach a normal state but a modulated superconducting state which remains down to T =0 with superconducting lamella, centered on magnetic domain walls, of thickness decreasing down to about ξ ≅200 A. 3. iii) The low temperature induced superconductivity corresponds to a true phase with bulk superconductivity which is realized because of the existence of a large demagnetizing field. 4. iv) A preliminary ( H, T ) magnetic phase diagram.