ANTIFERROMAGNETISM AND SUPERCONDUCTIVITY IN RBA2CU3O6+X (R = Y, TM, LU)

The effect of antiferromagnetic ordering on the normal-state and super conducting properties of RBa2Cu3O6+x (R = Y, Tm, Lu) single crystals i s studied. Precision resistivity measurements were used to probe the i nteraction between current carriers and the magnetic subsystem. Antife rromagnetic ordering is shown to impart dielectric properties to the s ystem. In oxygen-deficient (x < 0.4) crystals, prominent anomalies in the temperature dependences of resistivity are revealed around 160 K, which are accompanied by relaxation processes down to 120 K. These ano malies are found to be of a magnetic nature and are tentatively attrib uted to electronic phase separation on a microscopic scale. The experi mental results obtained suggest that the dielectric-metal phase transi tion in RBa2Cu3O6+x is of a percolative nature.