The magnetic behaviour of Dy$_2$Ir$_2$O$_7$ -- beyond the mean field approximation

The magnetic properties of pyrochlore iridate Dy2Ir2O7 prepared by CsCl flux method were investigated by means of heat capacity and magnetization measurements. The low temperature behaviour was confirmed to be consistent with previously published results, whereas the high temperature data and their analysis are presented for the first time. The bifurcation of zero field-cooled and field-cooled magnetization curves coincides well with the onset of the anomaly in specific heat pointing to an ordering of the iridium sublattice. We confront the previously determined Dy3+ CF scheme with our high-temperature magnetization and specific heat data. The difference between calculations and experimental data, represented by 20 K specific heat anomaly, suggests the behaviour beyond the mean field approximation. The Dy2Ir2O7 differs from the rest of the heavy rare-earth pyrochlore iridates, where the mean field approximation constitutes an adequate description. The deeper understanding of the Dy2Ir2O7 magnetic behaviour requires, among others, also the phonon spectra studies.