Anomalous behavior of the second magnetization peak inLa1.81Sr0.19CuO4single crystals: Possible influence of two-band superconductivity

We report an anomalous temperature $T$ variation of the field ${H}_{\text{on}}$ for the onset of the second magnetization peak in ${\text{La}}_{1.81}{\text{Sr}}_{0.19}{\text{CuO}}_{4}$ single crystals with the external magnetic field $H$ oriented parallel to the $c$ axis. While the peak field ${H}_{p}$ has a continuous decrease with increasing $T$, ${H}_{\text{on}}$ exhibits a sudden decrease for $T\ensuremath{\sim}11--15\text{ }\text{K}$. This behavior appears to be related to the particular $T$ dependence of the superfluid density in the case of two-band superconductivity affecting the $T$ variation of the elastic energy of the vortex system at low $H$.