Polarized Positrons as Spin Detectors for Paramagnetic Centres in Solids

A technique for studying paramagnetic defects in insulators or semiconductors acting as positron traps is presented. The spin polarization of the paramagnetic electrons of such centres can be determined by investigating the annihilation of spin-polarized positrons, e.g. by Doppler broadening (DB) or positron lifetime measurements. The viability of this technique is demonstrated by measuring the temperature dependence of the polarization of the paramagnetic electrons in F centres in KCl in high magnetic fields (± 4.5 T)