Strain state evolution and thickness-dependent properties of epitaxial Nd0.7Sr0.3MnO3 films

Nd0.7Sr0.3MnO3 (NSMO) films 7-300 nm thick have been grown on (001)(LaAlO3)(0.3)(Sr2AlTaO6)(0.7) (LSAT) and (001)SrTiO3 (STO) substrates, with lattice mismatches of 0.33% and 1.29%, respectively. The strain state evolution was examined fully by x-ray reciprocal space maps, in order to clarify its impact on the thickness-dependent properties of the films. It was found that all NSMO/LSAT films are coherently strained, having almost the same Curie (T-C) and peak resistivity (T-p) temperatures at fixed thicknesses, while the NSMO/STO films evolve from being fully strained to relaxed, showing inhomogeneous magnetic transitions and lower or higher T-C than their counterparts at 7-60 nm. The results underline that T-C (T-p) and phase separation are all controlled by the strain states of the films.