Relaxation of the electrical resistivity in Cr-doped Nd0.5Ca0.5MnO3 single crystals

Abstract

We have performed a systematic study of the time and temperature dependencies of the electrical resistivity (ρ(T,t)) in Nd 0.5Ca0.5Mn1-xCrxO3 single crystals with x = 0.02 and 0.07 in order to examine the dynamics of the phase separation. The relaxation effects can be described by the combination of a rapid exponential increase/decrease with a slower logarithmic contribution at longer times. The experimental results suggest the existence of a large temperature window in which huge relaxation effects occur, and the relative fraction of the coexisting phases rapidly changes as a function of time, depending on the initial magnetic state of the sample. The ρ(T,t) relaxation measurements were shown to be a suitable tool for probing the dynamical nature of the phase separation, in which magnetically distinct phases compete against each other in a wide temperature range. In addition, the features observed in the ρ(T,t) curves were found to be in excellent agreement with both the magnetic properties and the structural transitions observed in these manganites.