Thickness dependence of the stability of the charge-ordered state in Pr0.5Ca0.5MnO3 thin films

Thin films of the charge-ordered (CO) compound Pr0.5Ca0.5MnO3 have been dep osited onto (100)-oriented SrTiO3 substrates using pulsed laser deposition. Magnetization and transport properties are measured when the thickness of the him is varied. While the thinner films do not exhibit any temperature-i nduced insulator-metal transition under an applied magnetic field up to 9 T , for thickness larger than 1100 Angstrom a 5 T magnetic held is sufficient to melt the CO state. We have established the temperature-field phase diag ram and compared it to the bulk material. It indicates that the robustness of the CO state in thin films depends strongly on the strains and the thick ness. We proposed an explanation based on the distortion of the cell of the film.