Quenched Disorder-Controlled Resistive Relaxation in Near-Half-Doped Manganite Systems

We have investigated the influence of the disorder on the resistive relaxation effects in the Sm1-aSraMnO3 system where a is the fraction of the alkaline element. The disorder was introduced through chemical substitution of Mn sites with Fe doping, Ru doping, or forming composite structures by adding small fractions of BaTiO3. These three routes of adding disorder lead to a distinct behavior of Tc and T-MIT that depends on the concentrations and types of dopants. All the samples with a measurable zero-field resistive relaxation effect exhibited two peaks in the temperature dependence of the relaxation rates. In particular, a negative peak is found at low temperatures near the onset temperature of anti-ferromagnetic ordering while a positive peak is found near the metal-insulator transition temperature. In an attempt to quantify the strength of the disorder, we have determined the Delta T for each sample where Delta T is defined as the difference in the metal-insulator transition temperature (T-MIT) obtained from the warming and cooling curves in the temperature dependence of the resistivity. The magnitudes of the peaks increase in an exponential-like manner with the increasing thermal hysteresis width Delta T, which is a measure of the extent of the inhomogeneous magnetic state or disorder in the manganite system. On the other hand, the Ru substitution of Sm1-aSraMnO3 (SGSMO) reduced the thermal hysteresis width Delta T substantially and subsequently the relaxation rates. Our observations revealed a clear relationship between the quenched disorder and the resistive metastability in manganites.

Automated summary

The study investigated the influence of disorder on resistive relaxation effects in the Sm1-aSraMnO3 system, finding that different routes of disorder introduction lead to varied behaviors of Tc and T-MIT. The strength of disorder can be quantified by the difference in metal-insulator transition temperature. The observations revealed a clear relationship between quenched disorder and resistive metastability in manganites.