Investigation into Cation-Ordered Magnetic Polar Double Perovskite Oxides

The technique of coupling cation ordering with other microscopic degrees of freedom was employed to induce magnetic polar phenomena within the materials belonging to the double perovskite oxide family represented by the chemical formula AA′BB′O6, i.e., by considering double cation occupancy at both the 12- and 6-fold oxygen coordinated A- and B- cation sites. Starting from a paraelectric material, La2MnNiO6, that exhibits ferromagnetic behavior near room temperature, we constructed a wide chemical composition space to search for prospective polar magnetic systems. Since we have employed the hybrid improper mechanism of ferroelectricity to induce polar phenomena in these perovskite oxides, ensuring the stability of the cation ordering within certain octahedral rotational pattern was our primary imperative. Hence, we studied the energetics of (1) various A- and B- site cation-ordered phases, (2) cation-disordered phases, (3) various spin configurations, (4) various octahedral rotated structures, and (5) formation of double perovskite compositions with respect to their decomposition into possible stable compositions. On the basis of our study of a series of compositions comprising of transition metal ions from various periods at the B-site, we identify prospective compounds, those are expected to show both polar phenomena with a considerable polar distortion and ferro/ferri-magnetic properties with a considerable high magnetization.