Anne de Visser (Van der Waals-Zeeman Institute, University of Amsterdam)
In ferromagnets below the Curie temperature, TC, the electron spins align to produce a net magnetization. For a long time it was thought that superconductivity is incompatible with ferromagnetism. This is rooted in the microscopic BCS theory of superconductivity. The unusual coexistence of ferromagnetism and superconductivity, reported for UGe2 (under pressure), UIr (under pressure), URhGe and UCoGe, therefore attracts much attention. In superconducting ferromagnets the superconducting transition temperature Ts < TC and superconductivity and ferromagnetism are carried by the same 5f electrons. In this presentation I will focus on UCoGe (Ts = 0.8 K, TC = 3 K). µSR measurements provide unambiguous proof for the coexistence of superconductivity and ferromagnetism. The upper-critical field Bc2 is strongly anisotropic and provides evidence for an equal spin-pairing Cooper state and a superconducting gap function with axial symmetry. The response to pressure of the superconducting and magnetic phases shows superconductivity is enhanced near the magnetic quantum critical point.
|Other STFC||News||Site Sections||Important Links|