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Description
The data of the linear thermal expansion (α) and specific heat (Cp) are combined for the study the thermal and magnetic properties of PrBa2Cu3O6+x (PrBCO6+x or PrBCO) ceramic samples in two different oxygenation states: an underdoped (UN) with x = 0.44 and an optimally doped (OP) with x = 0.95. The temperature dependences of the ratio (α/Cp) as well as the effective Grüneisen parameter (Γeff), and the Pr magnetic contribution deduced using the (Δα(T)/T) and (ΔCp(T)/T) representations on the basis on the following differences ∆α = α(PrBCO6+x ‒ α(YBCO6+x) and ∆Cp = Cp(PrBCO6+x) ‒ Cp(YBCO6+x) have been calculated. Anomalies are detected at the Néel temperature TN = 9 and 14 K respectively for x = 0.44 and 0.95 due to the Pr antiferromagnetic (AFM) ordering. Below TN, there is evidence for some possible transitions at the spin reorientation temperature T2 = 6.75 K and 10.25 K, respectively for UN and OP states and close to the same low-critical point Tcr(x) = 4‒5 K. They are compared to the Schottky anomaly due to the crystal field splitting of the Pr3+ ground state in the OP state determined by numerical analysis and to earlier ∆Cp(T)/T-data obtained on an overdoped PrBCO7 ceramic sample [1]. The results show that below TN, the effect of the Pr-Cu(2) magnetic interaction to both AFM Pr and Cu(2) systems appears with more evidence as the key for a better interpretation of the unusual thermal properties of these nonsuperconducting PrBCO cuprates.
[1] Hilscher G, Holland-Moritz E, Holubar T, Jostarndt H.-D, Nekvasil V, Schaudy G, Walter U, Fillion G, “Valence of praseodymium in PrxY1−xBa2Cu3O7−δ: Inelastic-neutron-scattering, specific-heat, and susceptibility study,” Phys. Rev. B, vol. 49 (1994) 535.
| Submitters Country | Algeria |
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