Room temperature charge-ordered phase in Gd0.6Ca0.4MnO3 and Sm0.6Ca0.4MnO3 thin films

We have grown rarely studied Gd1-xCaxMnO3 (GCMO) and Sm1-xCaxMnO3 (SCMO) thin films on SrTiO3 (1 0 0) single crystal substrates with pulsed laser deposition in order to optimize the magnetic and structural properties for e.g. memristor-like applications. To enable the Mott insulator to metal transition with practicable external stimulus, the previously unstudied x=0.4 doping was chosen. The deposition temperature was 500 °C or 700 °C and the oxygen post-annealing was done in situ at 500 °C or 700 °C. All the films were fully textured and (0b0) oriented, but the ones made at 700 °C had better crystalline quality. For the same pulse amounts, GCMO films were clearly thinner than the SCMO films. Magnetically, all the films showed a charge/orbital order phase transition around 360 K and a ferrimagnetic transition around 70 K. The saturation magnetization at 10 K was highest in the films deposited and oxygen annealed at 700 °C. The samples deposited and annealed at 500 °C contained an unknown ferromagnetic impurity, which was invisible in structural characterization and not observed in the other samples. The samples made at 700 °C had a hysteretic I(V)-curves typical for materials used in memristors.