Growth of electronically distinct manganite thin films by modulating cation stoichiometry

Nd_1-xSr_xMnO₃ is a well-known manganite due to close connection among structure, transport, magnetism, and chemistry. Thus, it would be an ideal system to study the modification of physical properties by external stimuli including control of stoichiometry in growth. In this work, we show that an abrupt change of electronic and magnetic properties can be achieved by a subtle change of oxygen partial pressure in pulsed laser deposition. Interestingly, the pressure indeed modulates cation stoichiometry. We clearly observed that the films grown at 140 mTorr and higher showed clear insulator to metal transition and stronger magnetism, commonly found in less hole doping, while the films grown at 130 mTorr and lower showed insulating behavior and weak magnetism. From soft x-ray spectroscopic methods, we clearly observed the compositional difference in those thin films. This result is further supported by scattering of lighter elements in high oxygen partial pressure but not by anion deficiency in growth.