Phases competition in half-doped La0.5-xDyxCa0.5-ySryMnO3 films

Abstract

This paper reports the effects of substrate-induced strain on the high-quality La0.5-xDyxCa0.5-ySryMnO3 (0≤x≤0.2) (LDCSMO) films grown on (00l) SrTiO3 (STO) substrate. LDCSMO films were epitaxially grown on the STO substrate along [001] direction. The lattice parameter c of the film increases relatively with the thickness increasing, and the in-plane tensile strain was controlled by varying the film thickness. The Raman results at room temperature show that the in-plane Mn-O bond stretching and MnO6 distortion were suppressed by the in-plane tensile strain with the thickness of film decreasing. The magnetic results show that the CO-AFM insulating phase and the weak FM phase coexist at low temperature, and spin-glass effect was found in all films. The ferromagnetic order and insulating state were enhanced by tensile strain in thinner film. This abnormal enhancement of insulating state may be ascribed to the disordering state due to the stronger FM and AFM competition and the dominated “dead layer” in thinner film. The improved FM ordering is resulted from the increased double-exchange interaction for the MnO6 distortion suppressed by the in-plane tensile strain in thinner film. These results indicate spin-phonon coupling could be manipulated by controlling strain in manganese oxide films.