Control of magnetism in bilayer iridates

We have studied from first principles the magnetic properties of the bilayer perovskite iridates, A₃Ir₂O_7. In Sr₃Ir₂O₇, an easy c-axis collinear antiferromagnetic structure have been reported, a significant constrast to single layer Sr2IrO4 with in-plane canted moments. This behavior is understood by competition among intra- and interlayer bond-directional pseudodipolar interactions. Here we suggest two ways to control magnetic structure of the system from our first-principles calculations.. At first, we show that these two energy scales are controllable via epitaxial strain to drive spin-flop transition. Secondly, we suggest Ca-doping of Sr₃Ir₂O₇ could derive hybrid improper ferroelectricity to show strong magnetoelectric coupling effect.