Local magnetization study of the first-order superconducting transition in CeCoIn 5

Abstract

We report local magnetization measurements on the heavy fermion superconductor CeCoIn 5 using a micro-Hall probe. Below a critical point T 0 ( ∼ 0.8 K ), the local magnetization shows a clear jump at the superconducting transition temperatures for both H ∥ a and H ∥ c , indicating that the phase transition at the upper critical field H c 2 becomes a first-order phase transition. In addition, we observed an undershoot behavior of magnetization jump above μ 0 H ∼ 4.75 T ( H ∥ c ), which suggests a rapid change of textured superconducting structure with vortices and the nodal planes expected in the Fulde–Ferrell–Larkin–Ovchinnikov state.