Cu(2) Nuclear Resonance Evidence For A Magnetic Phase In Aged 60-K Superconductors Rba2cu3o6+X (R=Tm, Y)

It is widely believed that the long-range antiferromagnetic order in the RBa2Cu3O6+x compounds (R=Y and rare earths except for Ce, Pr, Tb) is totally suppressed for the oxygen index x greater than or equal to 0.4 (antiferromagnetic insulator-metal transition). We present the results of the copper nuclear quadrupole resonance/NMR studies of aged RBa2Cu3O6+x (R=Tm,Y) samples showing that a magnetic order can still be present at oxygen contents x up to at least 0.7 and at temperatures as high as 77 K.