Manipulation of the ferromagnetic domains of a manganite using an electric field.

We have measured the response of the fluid like phases$^{1}$ of ferromagnetic metal (FMM) and charge ordered insulator (COI) in thin films of the manganite (La$_{0.4}$Pr$_{0.6})_{0.67}$Ca$_{0.33}$MnO$_{3}$ (LPCMO) to an external electric field. The electric field (set by applying a voltage difference across the material) alters the fluid phases and increases the conductivity of the material by about 2 orders of magnitude above a threshold voltage$^{2}$. To check if the enhanced conductivity is associated with an increase in the size of the FMM domains, we measured the magnetization of the thin films using a SQUID magnetometer with and without an applied electric field. The saturation magnetization remained the same in either case showing that the FMM domains do not increase in size, which led us to hypothesize that the domains are just reoriented by the electric field. This hypothesis was verified by measuring the transverse resistance while a voltage difference was applied longitudinally across the material. At a threshold voltage when the longitudinal resistance decreased by about 2 orders of magnitude, the transverse resistance showed a small increase. This increase in resistance was attributed to the FMM domains being stretched in the direction of the electric field. [1] P. A. Sharma et al., Phys. Rev. B 71, 224416 (2005), [2] Tara Dhakal, et. al, Cond-mat/0607502.