ANOMALOUS SPIN-LATTICE RELAXATION IN INPFE3+ AND BAFBREU2+ EXAMINED WITH OPTICAL-DETECTION OF ELECTRON-PARAMAGNETIC RESONANCE

The Eu2+ defect in BaFBr and the Fe3+ defect in InP were investigated by optical detection of electron paramagnetic resonance (ODEPR). For both defects allowed (DELTAm(s) = +/-1) and forbidden (DELTAm(s) = +/-2) ODEPR transitions were observed. Some of the allowed ODEPR transitions showed an anomalous change of sip indicating a spin polarization enhancement. This anomalous behaviour of both spin systems (S = 7/2 for Eu2+ in BaFBr and S = 5/2 for Fe3+ in InP) arises from spin-lattice relaxations within the Eu2+ and Fe3+ Zeeman levels which operate faster for forbidden (DELTAm(s) = +/-2) transitions than for allowed transitions. Using the appropriate rate equations describing the two spin systems and taking into account strong forbidden spin-lattice relaxations, the measured ODEPR effects were explained.