Phase diagrams of strained Ca_1-xCe_xMnO₃ films

The transport and magnetic properties were examined of thin films of the electron-doped manganite Ca_1-xCe_xMnO ₃ (CCMO; 0≤x≤0.1) deposited on three different single-crystalline oxide substrates: YAlO₃, NdAlO₃, and LaSrAlO₄, which subject the films to a compressive strain, a practical lattice matching, and a tensile strain, respectively. The temperature dependence of the activation energy extracted from the resistivity-temperature curves clearly indicated the phase transitions in the CCMO films. A comparison with magnetization measurements revealed that regardless of the substrates, the temperature-driven phase transition of the CCMO films changed from the G-type antiferromagnetic transition at x=0 to the canted antiferromagnetic transition and to the charge- and/or orbital-ordered transition, as x was increased. In the canted antiferromagnetic phase, the epitaxial strains have significant impact not only on the transport properties but also on the magnetic properties such as the spontaneous magnetization and the magnetic anisotropy, confirming that the competition between antiferromagnetic super-exchange and ferromagnetic double-exchange interactions results in the canted antiferromagnetic state in the electron-doped CCMO films. Based on the results of the transport and magnetic measurements, the temperature versus band-filling phase diagrams of the strained CCMO films on three different substrates were established.