Photomagnetism and photoluminescence (PL) of (Pb–Fe–e −) complex in lead magnesium niobate–lead titanate (PMN–PT) crystals containing β-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)O 3–PbTiO 3 (PMN–PT), containing nanoparticles/wires of orthorhombic β-PbO as identified by Raman spectroscopy. Photo-EPR studies of the sample containing β-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 Fe 3+, photoinduced Pb 3+ 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 β-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 β-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.