Effect of strain on the phase separation and devitrification of the magnetic glass state in thin films of La_5/8-yPr_yCa_3/8MnO₃ (y= 0.45)

Abstract

We present our study of the effect of substrate induced strain on La_{5/8 - y}Pr_yCa_3/8MnO₃ (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.