Detection of Phase Transitions in Phase Separated (La_1-yPr_y)_1-xCa_xMnO₃ Thin Films

Phase separated manganites have competing phases that each have unique electronic, magnetic, and structural properties. The similar free energies these phases possess allow for the manipulation of phase transitions with the application of external stimuli. Here we report the role of an external magnetic field and a change in chemical doping ratios on the phase transitions in (La_1-yPr_y)_1-xCa_xMnO₃ thin films grown on NdGaO₃. These thin films showed that the nucleation and growth of ferromagnetic metallic regions in an anti-ferromagnetic charge ordered insulating background occurs at a higher temperature when an external magnetic field is applied. At a high enough field strength, these ferromagnetic metallic regions hinder the phase transition from paramagnetic insulating to anti-ferromagnetic charge ordered insulating phase which occurs at a relatively high temperature (close to 200 K). The value of the activation energy for the anti-ferromagnetic charge ordered insulating phase calculated by fitting the resistance vs. temperature data to the Arrhenius equation agrees with direct measurements taken using scanning tunneling spectroscopy.