COMPARISON OF STRONTIUM-INDUCED AND OXYGEN-INDUCED HOLES IN LA2CUO4

The Hall coefficient, dc conductivity, and hence the mobility, as well as the ac conductivity and the dielectric constant in the CuO2 planes are reported for single crystals of La2CuO4 containing ∼0.2 mole % holes introduced by doping with oxygen or strontium. In general, the transport properties are quite similar for the two kinds of acceptors. A smaller value of the binding energy is found for the Sr acceptor than the oxygen acceptor. In addition, the in-plane dielectric constant is found to be larger in the Sr-doped sample, and the characteristic temperature for variable-range hopping is smaller. The latter observations indicate that the radius of the hole's orbit when bound to the acceptor is larger for Sr than for O, consistent with the smaller binding energy. Despite these differences in the bound states of the acceptors, the holes introduced by O and Sr appear to affect the antiferromagnetic order in the same way since the two crystals have the same Néel temperature. The temperature dependencies of the in-plane mobility for the two systems are very similar, and are well-described by a simple model combining polar optical phonon scattering and the scattering of charged impurities. The quantitative agreement with theory for the optical phonon scattering confirms the polaronic nature of the charge carriers. © 1995 The American Physical Society.