Ultrasonic experiments on the high-Tc-superconductor Y2−xBaxCuO4−δ

Abstract

Abstract Sound velocity measurements on a mixed-phase sample Y 1.2 Ba 0.8 CuO 4−δ in high magnetic fields are reported. Like in normal metals, but in contrast to single-phase samples, the material is found to harden on cooling. In the vicinity of 95 K an elastic instability is observed which is referred to a semimetal-metal transition. For B 0 = 6T an anomalously large softening of ∼460 ppm is found at T c ( B 0 ). The importance of internal strains for the elastic behaviour and for the appearance of pronounced hysteresis effects in single-phase samples is discussed.