Interplay between magnetism and superconductivity in URhGe

Abstract

The magnetization rotation transition occurs in the itinerant ferromagnet URhGe when the field about 12T is applied in direction perpendicular to spontaneous magnetization in the plane of the smallest magnetic anisotropy energy.The transition is accompanied by the maximum of resistivity in the normal state and by reentrance of superconductivity at lower temperatures in the field interval between 8 and 13 Tesla [F.Levy et al, Science, to be published (2005)]. We discuss the magnetization orientation transition and the modification of triplet pairing superconducting state coexisting with ferromagnetism up to the fields about 2 Tesla and then reappearing in the broad vicinity of the transition. The nonsymmorphic space group crystal symmetry of ferromagnetic URhGe allows existance of antiferromagnetic ordering of magnetic moments of pairs of uranium atoms along a-axis. We show that the amplitude of this weak antiferromagnetic ordering increases below the phase transition into superconducting state due to Cooper pairs spontaneous magnetism.