POLARIZED POSITRONS AS SPIN DETECTORS FOR PARAMAGNETIC CENTERS IN SOLIDS

A technique for studying paramagnetic defects in insulators or semicon ductors acting as positron traps is presented. The spin polarization o f the paramagnetic electrons of such centres can be determined by inve stigating the annihilation of spin-polarized positrons, e.g. by Dopple r 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 (+/-4.5T).