Photoactive Pb³⁺host lattice ions in photorefractive Pb₅Ge₃O₁₁investigated by magnetic resonance techniques

Abstract

In photorefractive Pb 5 Ge 3 O 11 and (Pb 0.98 Ba 0.02 ) 5 Ge 3 O 11 crystals, Pb 2+ host lattice ions can be recharged by visible light to Pb 3+ . The magnetic and structural properties of this hole-trapping centre, metastable at low temperatures, are characterized by means of electron paramagnetic resonance. The axial gparameters are found to be g ⊥ = 2.0005(4) and g = g ⊥ + 0.0064(3) and the 207 Pb hyperfine interaction constants are A ⊥ = 34.77(5) and A = 34.64(5) GHz. This information is correlated with optical properties derived from optically detected magnetic resonance via the magnetic circular dichroism of the absorption. In this way, broad photochromic absorption bands extending from the band edge to 1.9 eV can be attributed to the Pb 3+ centre. Several observations give evidence that the Pb 3+ centre is involved in the holographic recharging effects observed in lead germanate.

Magnetism in a 2D Hybrid Ruddlesden–Popper Perovskite through Charge Redistribution Driven by an Organic Functional Spacer

“…It is possible to infer that the observed EPR signal can only be assigned to the paramagnetic states of lead. Such behavior could be presented by lead in valence Pb 1+ (6p 1 species) with g varying from 1 to 1.7 or Pb 3+ (6s 1 species), with g around 2 . No EPR signal was detected on the 3D pristine MAPbI 3 sample without histidine, as shown Figure (c).…”

Optical and X-ray photoelectron spectroscopy of PbGeO3 and Pb5Ge3O11 single crystals

“…A higher binding energy value of Pb4f 7/2 for set 2 indicates that some of the Pb +2 ions are oxidized to higher oxidation state, the concentration of which is more in LGO-2. Indeed evidence of the formation of Pb 3+ lattice ions in LGO-2 crystal under an illumination of 100 W Xe lamp has been reported in literature (Reyher et al 2001). Thus, Pb4f 7/2 core levels are the ones which are modified in both the crystals on irradiation.…”

“…The compositions, PbGeO 3 (LGO-1) and Pb 5 Ge 3 O 11 (LGO-2), both exhibit ferroelectric properties. Consequently, efforts were made during seventies to grow LGO-2 single crystals of high quality and characterize them for growth related defects and photorefractive, electro-optic and pyroelectric properties (Iwasaki et al 1971a, b;Bichard et al 1972;Houlton et al 1975;Goswami et al 1998;Yue et al 1998;Reyher et al 2001). Besides, several chemical substitutions for tetrahedral oxygen coordinated Ge 4+ ion or in the large Pb polyhedral were also attempted to improve the pyroelectric sensitivity of LGO-2 (Iwasaki et al 1972;Watton et al 1976;Bush and Venevtsev 1979;Otto et al 1980;Landolt-Börnstein 1982;Talik et al 2006).…”

Photo-magnetism and possible optical switching in Fe3+: PMN-PT: A Photo-EPR investigation

“…The presence of g=4.3 line, characteristic of dilute Fe 3+ ions, in the pink sample and its marginal increase in intensity on laser exposure suggests the new intense line at g=2 is not due to Fe 3+ . Reyher et.al [16] have reported a photo induced Pb 3+ center (g=2.00) in ferroelectric Pb 5 Ge 3 O 11 at low temperature. Due to sharpness of lines they, observed hyperfine lines due to 207 Pb (22.1% abundance), at 550mT and 1100mT.…”