Strain induced Co/Mn ionization and magnetic properties in double-perovskite Nd2CoMnO6 thin films

Abstract

The double-perovskite Nd2CoMnO6 (NCMO) thin films were epitaxially grown on LaAlO3 and SrTiO3 substrates with different orientations by the polymer-assisted deposition technique. A well crystallization quality of the films is confirmed by x-ray diffraction. The magnetism measurement suggests that all the films have a single ferromagnetic (FM) transition, but its substrate-orientational dependence is different from those in normal perovskite ABO3. By the analysis of the valence states of cations combining with the single FM transition, we suggest that the ionization degree of Co and Mn can be stimulated under both tensile and compressive strain, which can weaken the magnetic interaction. Thus, there are two aspects that competitively affect the magnetism [M(T) and Tc] of the NCMO film, i.e., the variation of oxygen octahedron similar to that in the normal perovskite ABO3 film and the degree of Co/Mn ionization, without changing the order of Co–O–Mn chain arrangement, resulting in the different orientation-dependent magnetism in NCMO films from that normally observed in ABO3 films. Our results give a systematic understanding of the substrate-induced-strain influence on the magnetic interaction in NCMO thin films and widen its practical application.