Nonlinear conduction in charge-ordered Pr 0.63 Ca 0.37 MnO 3 : effect of magnetic fields

Nonlinear conduction in a single crystal of charge-ordered $Pr_{0.63}Ca_{0.37}MnO_3$ has been investigated in an applied magnetic field. In zero field, the nonlinear conduction, which starts at $T<T_{CO}$, can give rise to a region of negative differential resistance (NDR) which shows up below the Neel temperature. Application of a magnetic field inhibits the appearance of NDR and makes the nonlinear conduction strongly hysteritic on cycling of the bias current. This is most severe in the temperature range where the charge-ordered state melts in an applied magnetic field. Our experiment strongly suggests that application of a magnetic field in the charge-ordering regime causes a coexistence of two phases.