Critical fluctuations in the spin-orbit Mott insulator Sr3Ir2O7.

ABSTRACT

X-ray magnetic critical scattering measurements and specific heat measurements were performed on the perovskite iridate [Formula see text]. We find that the magnetic interactions close to the Néel temperature [Formula see text] are three-dimensional. This contrasts with previous studies which suggest two-dimensional behaviour like Sr2IrO4. Violation of the Harris criterion ([Formula see text]) means that weak disorder becomes relevant. This leads a rounding of the antiferromagnetic phase transition at [Formula see text], and modifies the critical exponents relative to the clean system. Specifically, we determine that the critical behaviour of [Formula see text] is representative of the diluted 3D Ising universality class.