ANOMALOUS FREQUENCY-SHIFT OF NEGATIVE MUON SPIN PRECESSION IN N-TYPE SILICON

The dependence of the residual polarization of negative muons in n-typ e Si with impurity concentration (1.6 +/- 0.2) x 10(13) cm(-3) on temp erature in the 10-300 K range has been investigated. Measurements were carried out in external magnetic field of 0.08 T transverse to the mu on spin. Muon spin relaxation and frequency shift were observed at tem peratures below 30 K. The relaxation rate at 30 K is equal to 0.25 +/- 0.08 mu s(-1). The frequency shift at 20 K is equal to 7 x 10(-3). Bo th the relaxation rate and the frequency shift grow with decrease of t emperature. Below 30 K the relaxation rate is well described by the de pendence Lambda = bT(-q), where q = 2.8. An analysis of present and ea rlier published data on behavior of negative muon polarization in sili con is given. A possible mechanism of relaxation and frequency shift o f muon spin precession in silicon is considered.