Magnetic-field-induced metal-insulator phenomena in Pr1-xCaxMnO3 with controlled charge-ordering instability

Field-induced insulator-to-metal transitions have been found in Pr_1-xCa_xMnO₃ (0.3<=x<=0.5) single crystals, which are accompanied by a melting of the insulating charge-ordered (i.e., Mn³⁺/Mn⁴⁺ ordered) state. The transition is of the first order with a hysteresis and is even irreversible at low temperatures. The x-dependent metal-insulator phase diagrams in the H-T plane indicate that a deviation of x from 0.5 modifies the robustness of the charge-ordering state, which is argued in terms of the effect of discommensuration of the charge concentration on the charge-ordered state.