EFFECT OF GA DOPING ON THE ELASTIC PROPERTIES OF GDBA2CU3O7-DELTA HIGH T-C SUPERCONDUCTOR - AN ULTRASONIC STUDY

A detailed study of the effect of Ga doping on the high T-c supercondu ctor GdBa2Cu3O7 - delta has been carried out using ultrasonic techniqu e. Ultrasonic velocity and attenuation in samples with the general for mula GdBa2(Cu1 - xGax)(3)O-7 - delta With x = 0, 0.02, 0.04, and 0.06, respectively, have been mea sured as a function of temperature down t o T-c. Results indicate that these samples undergo an orthorhombic to tetragonal transition with Ga doping. For Ga doping up to 4 at%, the s tructure is orthorhombic, whereas for higher values of Ga doping, it h as tetragonal structure. Anomalies in velocity and attenuation in the 150 to 200 K range observed in samples with x less than or equal to 0. 04 is attributed to structural anomalies in the orthorhombic state. Th e results are discussed in detail considering the results reported by earlier workers on these samples.