Phase separation and persistent magnetic memory effect in La _0.625Ca_0.375MnO₃ and La_0.375Pr _0.25Ca_0.375MnO₃ films

Both La_0.375Pr_0.25Ca_0.375MnO₃ (LPCMO) and La_0.625Ca_0.375MnO₃ (LCMO) were found to exhibit coexistence of competing orders (phase separation) over a wide temperature range. However, substantial hysteretic behaviors in both of the temperature-dependent resistance [R (T)] and magnetization [M (T)] [also known as the persistent magnetic memory effect (PMME)] are only displayed in LPCMO. The results indicate that, in LPCMO, the size distribution of the coexisting charge-ordered insulating and metallic ferromagnetic (FM) phases plays a determinant role in the PMME effects in different temperature regimes. Moreover, due to the direct competition between the two coexisting phases, the system is most susceptible to the external applied field in the hysteretic temperature region. On the other hand, in LCMO, the phase transition between paramagnetic and FM is more like an isomorphic transition in pure materials, and thus does not show significant hysteresis.