Manipulating the magnetic domains of hole-doped manganites by using electric field

The observation of colossal magnetoresistance (CMR) and phase coexistence in hole-doped rare earth manganese oxides (manganites) have sustained the interest in these materials for over a decade. In recent years giant magneto resistance (GMR) materials have got recognition in the field of nanotechnology such as read/write memory devices. Because of the ever increasing demand of memory devices, researchers and engineers are compelled to look for new materials and reduce the device sizes even further. We investigate on the nanometer-sized phases co-existing in these manganites by using magnetotransport and scanning tunneling microscopy (STM) measurements. As thin films are required for industrial applications, we have grown thin films of manganites by using pulsed laser deposition on various substrates to obtain diverse physical properties. We will present the temperature dependence of the in-plane resistivity and the current to voltage (I-V) characteristics of these materials. While cooling and warming, resistivity of the manganites we grew shows hysteresis which is a signature of first order phase transition and phase coexistence.;We will present an unconventional method (magnetic field being conventional one) to tune one phase over another by applying electric field. This method is unique in that it can be applied precisely to the local phases unlike magnetic field which affects the whole region of application. In an attempt to identify the different phases, we were able to draw a simple but unique phase diagram by using resistance vs. magnetic field (R-H) isotherms. The phase diagram contains two clean phases (metallic and insulator) and two mixed phases (static phase and fluid phase). Our results show a visibly distinct effect of the applied electric field in the region of the phase diagram where it is fluid phase. We call this fluid like phase an electric soft matter state. Our data suggest that the applied electric field orients the metallic domains of the material in the direction of the applied field. Using this electric field driven orientation we have been able to suggest a method to manipulate the magnetic nanostructure of manganites. In addition we will also attempt to obtain a local electronic picture of the material by using a technique called scanning tunneling potentiometry.