Magnetic Resonance below Tc in the Oxygen-Deficient Rba2Cu3OX Superconductors
In this paper we report on the observation of a vei7 strong magnetic resonance (MR) signal below TC in the oxygen-deficient RBa2Cu3Ox (R=Y, Gd) crystals. The crystals were grown by the method of rf melting in a cold container, followed by a heating treatment of blocks obtained by melting at 700–900°C in air. Crystals with oxygen concentrations X<6.5 (nonsuperconducting), X≈6.5 (TC=50K) and X>6.5 (TC=90K) were studied. Fig. 1 shows the MR signals in GdBa2Cu3Ox crystals with TC=50K and TC=90K for two orientations of the magnetic field. The observed signals are characterized by a high intensity, the concentration of the MR centers is of the order of 4021 and can not be explained on the basis of impurities. The same signal of MR is observed in YBa2Cu3Ox. so it must be associated with ions of the host lattice, i. e. copper or oxygen.