SYNTHESES, MAGNETIC AND TRANSPORT PROPERTIES OFNbSr2(RE1.5Ce0.5)Cu2O10; RE = Tb,Ho,Er SERIES

摘要

The structural, magnetic and transport/electric properties of 1222-type niobio-cuprates, NbSr2(RE1.5Ce0.5)Cu2O10; RE = Tb,Ho,Er compounds prepared by high pressure and high temperature synthesis conditions have been investigated and discussed briefly. In order to obtain good samples, several samples have been prepared under wide synthesis conditions between 1250C and 1550C for 1–2 hours at a constant high pressure of 6 GPa. The samples synthesized under extreme conditions show that they have tetrago- nal crystal structure with I4/mmm as a possible space group. Neither superconductivity nor magnetic ordering are seen for RE = Tb in magnetic susceptibility measurements. On the other hand, the RE = Ho compound shows magnetic transition at around 30 K. This is due to the mixed magnetic state that arises from the main 1222 phase. The RE = Er compound reveals a ferromagnetic-like transition at 26 K. Unlike RE = Y, the magnetic properties of RE = Dy,Tb,Ho,Er compounds are found to be insensitive to the synthesis conditions. None of the samples showed zero resistance (bulk supercon- ductivity) transitions and all samples reveal semiconducting characteristics. The sam- ple with RE = Ho shows relatively low resistivity compared to the other two samples (RE = Tb, Er). All the samples show temperature and field dependence of magnetore- sistance about 1–6%. The nearly linear dependence suggests that hopping conduction is dominant in a certain temperature range for all the three studied compounds.