Magnetic structure and the crystal field excitation in heavy-fermion antiferromagnetic superconductor CePt3Si

Neutron scattering experiments have been carried out on the heavy fermion antiferromagnetic (AFM) superconductor CePt3Si with TN = 2.2 K and TSC = 0.75 K. We observed clear AFM Bragg reflections with Q0 = (001/2) below and above TSC, indicating microscopic coexistence of AFM order and heavy fermion superconductivity. The AFM structure, of two interleaved ferromagnetic sublattices of local Ce 4f moments, has inversion symmetry under simultaneous space–time reversal. However, hybridization with Pt and Si breaks this degeneracy and a combination of these two competing effects may be relevant to an understanding of the simultaneous occurrence of superconductivity and AFM order. The observed magnetic moment 0.16(1) μB/Ce is strongly reduced from the Curie–Weiss effective moment 2.54 µB/Ce. Clear crystal field excitations at 1 and 24 meV were observed. The magnetic susceptibility can be well explained in a level scheme assuming the Γ7 ground state, Γ6 and Γ7 first and second excited states, respectively.