An ultrasonic study of oxygen related structures in Nd123 between 80 and 400 K

This paper reports on an ultrasonic study at 130 kHz region in melt-textured Nd123, i.e. NdBa2Cu3O7−δ with different oxygen levels, i.e. δ=0, 0.2, 0.4, 0.6, 1. Three ultrasonic attenuation peaks were identified, which were related to oxygen levels in the material. An ultrasonic attenuation peak in the 360 K region was found at higher oxygen levels, i.e. δ=0.2, 0.4, and appeared to be a characteristic of the orthorhombic phase of the material. An ultrasonic attenuation peak in the 160 K region occurred at lower oxygen levels, i.e. δ=0.4, 0.6, while a peak close to 320 K was found in deoxygenated Nd123. All ultrasonic attenuation peaks showed the characteristics of structural changes. This proposal is supported by ultrasonic velocity measurements which displayed discontinuities at the corresponding temperatures.