Anomalies of the low-temperature specific heat of the cuprates La2CuO4 and La2−xMxCuO4 (M = Sr, Ba)

The low-temperature specific heat of the cuprates La2CuO4, La2−xMxCuO4 (M = Sr, Ba) in the temperature interval 2–45 K has been investigated by the technique of pulsed differential calorimetry. It is found that the coefficient of the residual linear term in the specific heat remains constant in the entire experimental temperature interval. It is shown that La atoms play a special role in the formation of the anomaly, associated with the specific nature of the interaction of these atoms with their environment, in the acoustic region of the phonon spectrum of these objects near 6 meV.