The time dependent response of the magnetic and transport properties of Fe-doped phase separated (PS) manganite ${\mathrm{L}\mathrm{a}}_{0.5}{\mathrm{C}\mathrm{a}}_{0.5}{\mathrm{M}\mathrm{n}\mathrm{O}}_3$ is reported. The nontrivial coexistence of ferromagnetic (FM) and non-FM regions induces a slow dynamics which leads to time relaxation and cooling rate dependence within the PS regime. This dynamics influences physical properties drastically. On one hand, metalliclike behavior, assumed to be a fingerprint of percolation, can be also observed before the FM phase percolates as a result of dynamical contributions. On the other hand, two novel effects for the manganites are reported, namely, the rejuvenation of the resistivity after aging and a persistent memory of low magnetic fields ($<1\mathrm{T}$), imprinted in the amount of the FM phase.

• Received 29 October 2001

DOI:https://doi.org/10.1103/PhysRevLett.89.137001