EPR study on higher oxygen pressure synthesized compound Pr2-xGdxCuO4

The electron paramagnetic resonance (EPR) and magnetic susceptibility measu rements were performed in Pr2-xGdxCuO4 (x = 0.02; 0.05) annealed at the hig her oxygen pressures of 15 and 21 bar. This annealing treatment causes a re duction of about 8% in the second order crystalline electric field (CEF) pa rameter \b(2)(0)\ at the Gd3+ site and leads to a drastic broadening of the Gd3+ resonance lines, which is consistent with spin relaxation processes o f Gd3+ due to the first excited state of Pt3+, increase in the CEF inhomoge neity upon doping and annealing, and an existence of Pr ions in both 3(+) a nd 4(+) oxidation states. The exchange coupling constants j(Pr-Pr) and j(Gd -Pr) are also estimated. (C) 1999 Elsevier Science Ltd. All rights reserved .