EPR STUDY OF THE HYPERFINE-STRUCTURE OF YB3-XYBXS, PB1-XYBXSE, AND PB1-XYBXTE SINGLE-CRYSTALS( ION IN PB1)

X-band (9.56 GHz) electron paramagnetic resonance (EPR) measurements w ere performed on Pb1-xYbxS, Pb1-xYbxSe, and Pb1-xYbxTe samples (x simi lar to 0.5-2%) at liquid-helium temperatures to study hyperfine transi tions, and to estimate the value of the effective Lande factor g and t he hyperfine-interaction constants of the two isotopes Yb-171 and Yb-1 73 possessing nonzero nuclear magnetic moments. The data indicated tha t the site symmetry at the Yb3+ ion in all the host crystals, Pb1-xYbx S, Pb1-xYbxSe, and Pb1-xYbxTe, is octahedral. The EPR line positions w ere found not to vary with the orientation of the external magnetic fi eld, indicating that the g tensors and the hyperfine-interaction tenso rs are isotropic. The Yb3+ Lande factors (g) were deduced to have the values 2.545 +/- 0.005, 2.585 +/- 0.005, and 2.525 +/- 0.005, respecti vely, in Pb1-xYbxS, Pb1-xYbxSe, and Pb1-xYbxTe. The calculated Lande f actors are slightly different from these; the degree of covalent bondi ng was estimated from the differences in the experimental and calculat ed Lande factors, The values of the hyperfine-interaction constants fo r Yb-171(3+) and Yb-173(3+) isotopes were estimated to have the values (171)A = 138 +/- 2 mT, (173)A = 39 +/- 1 mT in Pb1-xYbxSe, (171)A = 5 9 +/- 2 mT, (173)A = 19 +/- 1 mT in Pb1-xYbxTe, and (171)A = 60 +/- 2 mT in Pb1-xYbxS.