Anomalous local magnetic shielding effect at muon site in Sr2.5Ca11.5Cu24O41 and Ce0.99Cu2.02Si2

We present that the time structure of ZF- and LF-mu SR spectra in the magne tic phase of Sr2.5Ca11.5Cu24O41 and in the A-phase of Ce0.99Cu2.02Si2 share s a number of common features. In particular, the magnitude of local magnet ic field at the muon site estimated from ZF-mu SR is seemingly far smaller than that estimated by LF-quenching experiment. As a microscopic model of s uch an anomalous local magnetic shielding, we discuss the possibility of mu on-induced local magnetism due to the magnetic instability of frustrated sp in systems near the quantum critical point. (C) 2000 Elsevier Science B.V. All rights reserved.