SYNTHESES, MAGNETIC AND TRANSPORT PROPERTIES OF NbSr2(RE1.5Ce0.5)Cu2O10; RE = Tb, Ho, Er SERIES

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 1250 degrees C and 1550 degrees C for 1-2 hours at a constant high pressure of 6GPa. The samples synthesized under extreme conditions show that they have tetragonal 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 30K. 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 similar to 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 superconductivity) transitions and all samples reveal semiconducting characteristics. The sample 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 magnetoresistance about 1-6%. The nearly linear dependence suggests that hopping conduction is dominant in a certain temperature range for all the three studied compounds.