The specific heat of $\mathrm{Pr}{\mathrm{Ba}}_2{\left({\mathrm{Cu}}_{1-x}{\mathrm{Ga}}_x\right)}_3{\mathrm{O}}_{7-\delta }$ ($x=0, 0.04, \mathrm{and} 0.08$; $\delta \sim 0.1$) in magnetic fields up to 8 T was studied. A depression of antiferromagnetic transition temperature $T_N$ for Pr ions with Ga substitution becomes evident through broad specific-heat anomalies peaked at 17, 14, and 10 K for $x=0, 0.04, \mathrm{and} 0.08$, respectively. Both the magnitude of the anomaly and the $T_N$ values can be suppressed with magnetic field as often observed in conventional antiferromagnetic transitions. The specific-heat data above or below $T_N$ increase with Ga substitution. In addition, by fitting them to $C=\frac{A}{T^2}+\gamma T+B{T}^3$ in the temperature range $0.6<~T<~5$ K, the linear term coefficient $\gamma$ of the specific heat increases with $x$ and decreases with magnetic field. These results suggest that the unusually large value of $\gamma$ in $\mathrm{Pr}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ may be partially due to the strong magnetic correlation among Pr ions.

• Received 14 November 1994

DOI:https://doi.org/10.1103/PhysRevB.52.15099