Disordered dimer state in electron-doped Sr3Ir2O7
Sr3Ir2O7 is an unusual manifestation of a bilayer square lattice of spins (as illustrated at top of the Figure) due to the extended exchange inherent to its 5d electron valence states and their large orbital extent, not only within but also between bilayer planes. As a result, this system potentially exists in a unique parameter space where the strength of magnetic exchange coupling between these planes can approach or exceed the strength of the coupling within them.