Low-temperature specific heat of the high-Tc superconductors La1.8Sr0.2CuO4−δ and RBa2Cu3O7−δ (R=Y, Eu, Ho, Tm, and Yb)
J. M. Ferreira, B. W. Lee, Y. Dalichaouch, M. S. Torikachvili, K. N. Yang, M. B. Maple
DOI 10.1103/PhysRevB.37.1580 · Physical Review B
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Abstract
Low-temperature specific-heat measurements have been carried out between 0.5 and 30–50 K on the high-Tc copper oxide superconductors La1.8Sr0.2CuO4−δ and RBa2Cu3O7−δ (R=Y, Eu, Ho, Tm, and Yb). The specific heat of the La1.8Sr0.2CuO4−δ and YBa2Cu3O7−δ compounds below Tc can be resolved into a contribution of the form Ce(T)=γ’T with a finite γ’ and a lattice contribution that consists of Debye and Einstein terms. Specific-heat data for the RBa3Cu3O7−δ compounds with R=Ho, Tm, and Yb exhibit no features due to magnetic order above 0.5 K, but reveal electronic Schottky anomalies associated with crystalline electric field (CEF) splitting of the Hund’s-rules ground-state multiplet of the R3+ ions. The Schottky anomalies can be described by calculations based on tentative energy-level schemes for the Ho3+, Tm3+, and Yb3+ ions in the CEF which are presented. Specific-heat data for the EuBa2Cu3O7−δ compound, which can be separated into a γ’T term, a Debye contribution, and a low-temperature upturn, are consistent with a nonmagnetic J=0 ground state for Eu3+, as expected from Hund’s rules.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| La1.8Sr0.2CuO4-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 35 | Pressure not reported | unknown |
| La1.8Sr0.2CuO4-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 35 | Pressure not reported | unknown |
| La1.8Sr0.2CuO4-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 35 | Pressure not reported | unknown |
| YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| EuBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| EuBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| EuBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| HoBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| HoBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| HoBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| TmBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| TmBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| TmBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| YbBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| YbBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
| YbBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 92 | Pressure not reported | midpoint |
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