Structural and metamagnetic transitions in thin films of Ce-doped Pr0.5Ca0.5MnO3 manganites

• Epitaxial films of Pr0.5 − xCexCa0.5MnO3 show structural transitions.
• Pr0.45Ce0.05Ca0.5MnO3 under compressive strain exhibit metamagnetic transition at 2 K.
• Epitaxial strain suppresses the metamagnetic transitions.
• Most films show pinched hysteresis indicating co-existed ferromagnetic phases at 2 K.

We have investigated the effects of Ce-doping, epitaxial strain and thickness variation on the physical properties of four series of manganite thin films of Pr0.5 − xCexCa0.5MnO3 (x = 0, 0.05, 0.10). Two series of films were deposited on LaAlO3 (001) substrates under compressive strain: one series with fixed thickness (~ 250 nm) and varied Ce-doping, and another series with constant Ce-doping (x = 0.05) and varied thickness. In similar manner, other two series of films were deposited on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) substrates with tensile strain. An important feature of this system is that the films (x = 0.05) deposited on LaAlO3 show coherent compressive strain till the thickness as large as 700 nm, albeit with a different structure. All the films under study are highly insulating and show unsaturated magnetic hysteresis loops with a very low magnetic moment (~ 0.6–0.7μB/f.u.). As we increase Ce-doping, a structural transition manifest in the films. At 2 K, small step-like metamagnetic transition appears in magnetic hysteresis of compressively strained films with x = 0.05. However, metamagnetic transition is absent in the films with tensile strain. Several films show pinched hysteresis loops indicating two co-existed ferromagnetic phases (soft and less soft) at low temperatures. The results are discussed in the framework of effects of Ce-doping, structural transition and epitaxial strain in thin films.