THERMAL-CONDUCTIVITY AND PHONON-SCATTERING MECHANISM IN LA(2-X)M(X)CUO(4)

The thermal conductivity kappa of high density La(2-X)M(X)CuO(4) (M = Ba, Sr) sintered materials was measured between 15K and 150K for the v arious concentrations of Ba and the phonon thermal conductivity was an alyzed comparing with that of Nd2-XCeXCuO4. The pretfy large kappa val ue for pure La2CuO4 was drastically diminished by substituting La by a small amount of Ba atoms especially at fowl temperatures. It wlas fou nd that a new type of the phonon scattering center such as a two-level tunneling must be taken account of in order to explain the observed k appa reduction.