Critical fluctuations in the spin-orbit Mott insulator Sr 3 Ir 2 O 7

Abstract

X-ray magnetic critical scattering measurements and specifc heat measurements were performed on the perovskite iridate Sr 3 Ir 2 O 7 . We fnd that the magnetic interactions close to the Néel temperature TN = 283.4(2) K are three-dimensional. This contrasts with previous studies which suggest two-dimensional behaviour like Sr 2 IrO 4 . Violation of the Harris criterion (dv > 2) means that weak disorder becomes relevant. This leads a rounding of the antiferromagnetic phase transition at TN, and modifes the critical exponents relative to the clean system. Specifcally, we determine that the critical behaviour of Sr 3 Ir 2 O 7 is representative of the diluted 3D Ising universality class.