INFLUENCE OF FLUORINATION ON THE TRANSPORT-PROPERTIES OF LA1.85-YSR0.15NDYCUO4 NEAR THE LOW-TEMPERATURE STRUCTURAL TRANSITION

The influence of fluorination on thermal conductivity, specific heat, magnetic susceptibility, electrical resistivity and thermoelectric pow er of La1.85-ySr0.15NdyCuO4 has been investigated. The temperature var iation of the thermal conductivity of the untreated samples with Nd ex hibits a change in slope just below the low-temperature structural tra nsition (LTO ---> LTT), which could be associated with strong phonon-e lectron interactions. The specific heat of the y = 0.2 unfluorinated s ample presents a jump near 50 K confirming the structural transition. Below 10 K, the specific heat of the two y = 0.8 samples (unfluorinate d or fluorinated) shows an important increase with decreasing temperat ure, presumably associated with some type of magnetic ordering in the Nd3+ ions. In addition to an increase of T(c), the fluorination proces s suppress the anomalies observed in the thermal conductivity.