Substitutional effect of Mg 2+ on structural and magnetic properties of La 2 Mg x Ni 1‐x MnO 6 double‐perovskite thin films

Abstract By doping different concentrations of Mg 2+ at Ni site, the (00 l )‐oriented La 2 Mg x Ni 1‐ x MnO 6 (abbreviated as LM x NMO, x = 0, 0.1, 0.2, 0.3, 0.4) double‐perovskite thin films were epitaxially grown by pulsed laser deposition. The substitutional effect of Mg 2+ on the structural and magnetic properties of the films is comprehensively investigated. It is found that with the increase of Mg‐doping concentration, the in‐plane and out‐of‐plane lattice constants as well as the cell volume of the LM x NMO thin films increase, which could be ascribed to the radius difference between Mg 2+ and Ni 2+ /Ni 3+ ions, resulting in the in‐plane compressive stress in LM x NMO films. When the Mg‐doping concentration is small ( x ≤ 0.1), the doped Mg 2+ tends to substitute Ni 3+ , which restrains the intensity of antiferromagnetic interaction between Ni 3+ ‐O‐Mn 3+ , resulting in the reduced the exchange bias field as well as the increased the saturation magnetization. However, when the Mg‐doping concentration increases to x ≥ 0.2, Mg 2+ becomes to mainly replace Ni 2+ position, which could inhibit the super‐exchange ferromagnetic interaction between Ni 2+ ‐O‐Mn 4+ magnetic paths and thus reduce the saturation magnetization. The enhanced magnetic properties can be obtained in the LM 0.1 NMO double‐perovskite thin film, with a large saturation magnetization of 492.12 emu/cm 3 and a high Curie temperature of 262.7 K.