POLARIZED POSITRONS AS SPIN DETECTORS FOR PARAMAGNETIC CENTERS IN SOLIDS

A novel technique for studying paramagnetic defects in insulators or s emiconductors acting as positron traps is presented. The spin polariza tion of the paramagnetic electrons of such centres can be determined b y investigating the annihilation of spin-polarized positrons, e.g., by Doppler-broadening or positron-lifetime measurements. The viability o f this technique is demonstrated by measuring the temperature dependen ce of the polarization of the paramagnetic electrons in F-centres in K Cl in high magnetic fields (+/-4.5 T).