title: Photomagnetism and photoluminescence (PL) of (Pb-Fe-e(-)) complex in lead magnesium niobate-lead titanate (PMN-PT) crystals containing beta-PbO nanoclusters.
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.
authors.affiliation: Department of Physics, Alabama A&M University, Normal, AL 35762, USA. sundarbairavarasu@gmail.com
authors.forename: Sundar R
authors.initials: SR
authors.lastname: Bairavarasu
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Edwards
authors.forename: Medury D
authors.initials: MD
authors.lastname: Sastry
authors.forename: Faris
authors.initials: F
authors.lastname: Kochary
authors.forename: Praveena
authors.initials: P
authors.lastname: Kommidi
authors.forename: B Rami
authors.initials: BR
authors.lastname: Reddy
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Lianos
authors.forename: Manmohan D
authors.initials: MD
authors.lastname: Aggarwal
mesh_terms: D001128:Argon / Q000737:chemistry; D003460:Crystallization; D004574:Electromagnetic Fields; D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D008027:Light; D008280:Magnetics; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods; D014025:Titanium / Q000737:chemistry*
chemical_list: D010087:Oxides; C404734:lead magnesium niobate; C481719:lead titanate; C511603:magnesium titanate; D009556:Niobium; D007854:Lead; C047365:lead oxide; D001128:Argon; D014025:Titanium; D007501:Iron; D010100:Oxygen