Local magnetization study of the first-order superconducting transition in CeCoIn5 Original Research Article

We report local magnetization measurements on the heavy fermion superconductor CeCoIn5 using a micro-Hall probe. Below a critical point T0T0 (View the MathML source∼0.8K), the local magnetization shows a clear jump at the superconducting transition temperatures for both H∥aH∥a and H∥cH∥c, indicating that the phase transition at the upper critical field Hc2Hc2 becomes a first-order phase transition. In addition, we observed an undershoot behavior of magnetization jump above View the MathML sourceμ0H∼4.75T (H∥cH∥c), which suggests a rapid change of textured superconducting structure with vortices and the nodal planes expected in the Fulde–Ferrell–Larkin–Ovchinnikov state.