Memorylike response of the magnetic glass

Abstract

Nonergodicity of phase coexisting state is not trivial, and its understanding is yet unclear. We have investigated two prototype manganites, ${\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{Mn}}_{0.975}{\mathrm{Al}}_{0.025}{\mathrm{O}}_{3}$ and ${\mathrm{La}}_{0.5}{\mathrm{Ca}}_{0.5}\mathrm{Mn}{\mathrm{O}}_{3}$ where ferromagnetic and antiferromagnetic phases coexist at low temperatures due to kinetic arrest of a first-order transition. We have studied the evolution of the dynamics of a kinetically arrested state with temperature and magnetic field. We also highlight a peculiar nonequilibrium behavior of the phase coexisting state that appears like the memory effect, which basically is an intrinsic property of spin glasses or related systems. If the volume fraction of the two coexisting phases is altered by changing magnetic field at a temperature ${T}_{m}$ during cooling, the phase fraction is fully or partially reacquired during heating above ${T}_{m}$ depending on which phase among the coexisting phases is the actual equilibrium phase of the system. We suggest that the memorylike response observed here is not due to competing exchange interaction, instead arises due to supercooling, superheating, and kinetic arrest of the associated transition. Such magnetic response provides an easy method of identifying the ground state of a kinetically arrested system.