Novel dynamical effects and persistent memory in phase separated manganites
The time dependent response of the magnetic and transport properties of Fe-doped phase separated (PS) manganite La$_{0.5}$Ca$_{0.5}$MnO$_{3}$ 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 drastically on physical properties. On one hand, metallic like 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 one, two novel effects for the manganites are reported, namely the rejuvenation of the resistivity after ageing, and a persistent memory of low magnetic fields ($<$ 1 T), imprinted in the amount of the FM phase. As a distinctive fact, this memory can be recovered through transport measurements.