Pressure effects on charge, spin, and metal-insulator transitions in narrow bandwidth manganite Pr${}_{1-x}$Ca${}_x$MnO${}_3$

Abstract

Pressure effects on the charge and spin states and the relation between the ferromagnetic and metallic states were explored on the small bandwidth manganite Pr${}_{1-x}$Ca${}_x$MnO${}_3$ (x = 0.25, 0.3, 0.35). Under pressure, the charge ordering state is suppressed and a ferromagnetic metallic state is induced in all three samples. The metal-insulator transition temperature (T${}_{MI}$) increases with pressure below a critical point P*, above which T${}_{MI}$ decreases and the material becomes insulating as at the ambient pressure. The e${}_g$ electron bandwidth and/or band-filling mediate the pressure effects on the metal-insulator transition and the magnetic transition. In the small bandwidth and low doping concentration compound (x = 0.25), the T${}_{MI}$ and Curie temperature (T${}_C$) change with pressure in a reverse way and do not couple under pressure. In the x = 0.3 compound, the relation of T${}_{MI}$ and T${}_C$ shows a critical behavior: They are coupled in the range of $\sim$0.8-5 GPa and decoupled outside of this range. In the x = 0.35 compound, T${}_{MI}$ and T${}_C$ are coupled in the measured pressure range where a ferromagnetic state is present.

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