Disorder-induced melting of the charge order inthin films of Pr0.5Ca0.5MnO3

Abstract

We have studied the magnetic-field–induced melting of the chargeorder in thin films of Pr0.5Ca0.5MnO3 (PCMO) films onSrTiO3 (STO) by X-ray diffraction, magnetization and transportmeasurement. At small thickness (25 nm) the films are undertensile strain and the low-temperature melting fields are of theorder of 20 T or more, comparable to the bulk value. Withincreasing film thickness the strain relaxes, which leads to astrong decrease of the melting fields. For a film of 150 nm, within-plane and out-of-plane lattice parameters closer to the bulkvalue, the melting field has reduced to 4 T at 50 K, with a strongincrease in the hysteretic behavior and also an increasingfraction of ferromagnetic material. Strain relaxation by growth onYBa2Cu3O7 − δ or by post-annealing yields evenstronger reduction of the melting field. Apparently, strainedfilms behave bulk-like. Relaxation leads to an increasing suppressionof the CO state, presumably due to an atomic-scale disorder producedby the relaxation process.