Characteristics of the magnetic order in CeCu₂Si₂ revealed by neutron spin-echo measurements

In antiferromagnetically ordered A-type CeCu₂Si₂ the linewidth of the magnetic Bragg peaks, measured by elastic neutron scattering, is larger than the resolution limit for T < T_c,ρ, with T_c,ρ identified by resistivity measurements as the onset of a very broad transition to the superconducting state. In contrast to that, the linewidth in A/S-type CeCu₂Si₂, where bulk superconductivity (SC) expels magnetic order, is resolution-limited. This suggests that filamentary SC limits the size of magnetically ordered regions in A-type crystals. We present neutron spin-echo measurements which yield significantly faster exponential decay rates of the normalized intermediate scattering function S(_AF,t)/S(_AF,0) in A-type CeCu₂Si₂ at T < T_c,ρ than at T_c,ρ < T < T_N as well as in A/S-type CeCu₂Si₂ at T < T_c. We conclude that filamentary SC also causes reduced lifetimes and enhanced fluctuation rates of the magnetic order in A-type CeCu₂Si₂.