Abstrakt
UCoGe is an archetype of coexisting weak itinerant 5f-electron ferromagnetism (T-C similar to 3 K, mu(s) = 0.03 mu(B)/f.u.) and superconductivity (T-SC similar to 0.6 K) at ambient pressure. The Ru substitution for Co leads to an initial sharp increase of the T-C up to the maximum of T-C = 8.5 K for x = 0.12, increase of spontaneous magnetic moment and suppression of superconductivity.
We have grown the UCo0.88Ru012Ge single crystal and studied magnetization along the principal crystallographic axes. To see the microscopic background of these findings we performed a polarized neutron diffraction experiment on D3 diffractometer in ILL.
We have found that the Co and U moments are parallel in UCo0.88Ru0.12Ge, in contrast to the antiparallel configuration in UCoGe. This is probably the reason of the spontaneous magnetization increase with Ru doping.