Evidence for the Coexistence of Superconductivity and the Magnetic A-Phase in CeCu₂Si₂ Proved by Muon Knight Shift

Abstract

Muon spin rotation measurements under high transverse fields (HTF-μSR) have been performed on polycrystalline samples of Ce_0.99Cu_2.02Si₂. The muon hyperfine coupling constant was determined to be -3.36 kOe/μ_B from a Knight shift (K) vs susceptibility (χ) plot for 2 K < T < 200 K, which is comparable to those for Cu and Si nuclei. Below ∼1 K, the Knight shift at the precession signal, showing broadening due to the magnetic A-phase, exhibited a reduction at 0.5 T, while it remained unchanged above 1.0 T, strongly suggesting the microscopic coexistence of superconductivity with the magnetic A-phase.