Photomagnetism and photoluminescence (PL) of (Pb-Fe-e(-)) complex in lead magnesium niobate-lead titanate (PMN-PT) crystals containing beta-PbO nanoclusters

Spectrochim Acta A Mol Biomol Spectrosc. 2008 Dec 15;71(4):1581-7. doi: 10.1016/j.saa.2008.06.004. Epub 2008 Jun 19.

Abstract

We present electron paramagnetic resonance (EPR)--evidence of photomagnetism under the conditions of in situ green laser illumination (photo-EPR) in lead magnesium niobate-lead titanate, Pb(Mg,Nb)O3-PbTiO3 (PMN-PT), containing nanoparticles/wires of orthorhombic beta-PbO as identified by Raman spectroscopy. Photo-EPR studies of the sample containing beta-PbO, brownish red in color, have shown intense line at g=2.00, and its yield increased when produced in the presence of 7.5 kG external magnetic field suggesting the formation of magnetic polaron. This was identified as due to interaction between Fe3+, photoinduced Pb3+ and unpaired electron trapped at oxygen vacancies. The photoinduced growth and decay of magnetic polaron has shown a non-exponential behavior. Photoluminescence (PL) studies were conducted with excitation at 308 nm (XeCl laser) and also at 454.5, 488 and 514.5 nm using Ar+ laser. The excitation with 308 nm gave broad PL centered at 500 and 710 nm the latter being quite prominent in beta-PbO containing crystals, along with cooperative luminescence at 350 nm involving two emitting centers. The excitation with Ar+ laser lines, close to the electronic absorption in samples containing beta-PbO gave richer and sharp PL emission in red region from the constituents of the magnetic polaron and also intense anti-Stokes emission on excitation with 514.5 nm radiation. This appears to be due to phototransfer optically stimulated luminescence (PT-OSL) involving electron-hole recombination at photoinduced magnetic polaron site.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Argon / chemistry
  • Crystallization
  • Electromagnetic Fields
  • Electron Spin Resonance Spectroscopy
  • Iron / chemistry*
  • Lead / chemistry*
  • Light
  • Magnetics*
  • Nanoparticles / chemistry*
  • Nanotechnology / methods*
  • Niobium / chemistry*
  • Oxides / chemistry*
  • Oxygen / chemistry
  • Spectrum Analysis, Raman / methods
  • Titanium / chemistry*

Substances

  • Oxides
  • lead magnesium niobate
  • lead titanate
  • magnesium titanate
  • Niobium
  • Lead
  • lead oxide
  • Argon
  • Titanium
  • Iron
  • Oxygen