Effect of strain on the phase separation and devitrification of the magnetic glass state in thin films of La5/8-yPryCa3/8MnO3 (y=0.45)

We present our study of the effect of substrate induced strain on La5/8-yPryCa3/8MnO3 (y = 0.45) thin films grown on LaAlO3, NdGaO3 and SrTiO3 substrates that show large scale phase separation. It is observed that unstrained films grown on NdGaO3 behave quite similarly to bulk material but the strained films grown on SrTiO3 show melting of the insulating phase to the metallic phase at low temperatures. However, the large scale phase separation and metastable glass-like state is observed in all the films despite differences in substrate induced strain. The measurements of resistivity as a function of temperature under a cooling and heating in unequal field (CHUF) protocol elucidate the presence of a glass-like metastable phase generated due to kinetic arrest of the first order transformation in all the films. Like structural glasses, these magnetic glass-like phases show evidence of devitrification of the arrested charge order antiferromagnetic insulator (CO-AFI) phase to the equilibrium ferromagnetic metallic (FMM) phase with isothermal increase of magnetic field and/or iso-field warming. These measurements also clearly show the equilibrium ground state of this system to be FMM and the metastable glass-like phase to be AFI phase.