ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Magnetic susceptibility measurements of high purity MgO single crystals (〈50-wt. ppm transition metals) by means of a vibrating-sample magnetometer shows an anomaly at 800 K. At the same temperature the electric conductivity increases anomalously, the static dielectric constant (large-closed-square) increases from 9 to ≈150, a pronounced positive surface charge appears, and Fe2+ in the MgO matrix oxidizes to Fe3+. The data are consistent with O2−2 (peroxy) defects, representing self-trapped, spin-paired positive holes at Mg2+ vacancy sites. Diamagnetic at low temperatures, the holes start to decouple their spins (approximately-greater-than)600 K, probably forming at first V0 centers (two O− at an Mg2+ vacancy), then V− centers (single O− at an Mg2+ vacancy), and releasing mobile O− states. These O− represent itinerant charge carriers on acceptor levels near the O 2p-dominated valence band and conduct by O−/O2− valency fluctuations. The O− concentration is of the order of 8 × 1019 cm−3.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.347807
