Phase coexistence and nonequilibrium dynamics under simultaneously applied magnetic field and pressure: Possible role of the interface

Strong spin-lattice coupling makes external pressure ($P$) an important parameter across a first-order magnetostructural phase transition. Here, we have studied the effect of $P$ under different magnetic fields on the phase coexistence and kinetics of nucleation and growth around such transitions in two prototype systems ${\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{Mn}}_{0.975}{\mathrm{Al}}_{0.025}{\mathrm{O}}_{3}$ and ${\mathrm{La}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}$, where the ferromagnetic-metal and antiferromagnetic-insulator phases compete in real space. We have determined the $H\ensuremath{-}P$ phase diagram of supercooling and superheating temperatures. The change in supercooling and superheating temperatures and the nucleation and growth control the phase coexistence. Surprisingly, despite having contrasting ground states, in both ${\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{Mn}}_{0.975}{\mathrm{Al}}_{0.025}{\mathrm{O}}_{3}$ and ${\mathrm{La}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}$ the transformation rate between the two states is suppressed at higher pressure. This proves that there must be some universal phenomena controlling the dynamics. Different spin and structural order at the interface of the two phases appear to be responsible for giving rise to strong frustration and eventually hindering the kinetics, resulting in the stabilization of glasslike behavior.