Anomalous thermal expansion of PrBCO compounds revisited at low temperatures

The low-temperature variations of the thermal expansion coefficient α(T) of a non-superconducting PrBa₂Cu₃O_6+x ceramic in two states of oxygenation, x = 0.44 and 0.95 are reanalyzed using the α(T)/T and a(T)/T² versus T representations. Below the Neel temperature TN of the Pr antiferromagnetic ordering which increases respectively from 9 to 14 K, two anomalies are observed. The first one is located at T2 ~ 6-7 and 9-10 K respectively, whereas the second one occurs independently of x near T_cr(x) ~ 4-5 K. The results are discussed and compared with earlier experimental and theoretical studies.