Temperature evolution of crystallographic parameters in pyrochlore iridates

The rare-earth iridates, with general formula A2Ir2O7 (A = rare-earth ion), crystallise in a pyrochlore structure. They display a wide range of exotic magnetic and electronic low temperature properties, dependent on the specific rare-earth ion, due to the inherent magnetic geometric frustration of the rare-earth and Ir4+ (J = ½) corner-sharing tetrahedral lattices. Surprisingly however, initial magnetic ordering of the Ir4+ sublattice appears to be primarily dependent on the A ion size, rather than the rare-earth’s specific electronic properties. To investigate this relationship, we have measured the lattice compressibility and the structural evolution with pressure of several A2Ir2O7 members at room temperature and 20 K (ESRF, ID15b, HC-4856). To corroborate our very recent results, the temperature evolution of structural parameters is proposed to be investigated. We request beam time to use synchrotron powder X-ray diffraction and ID22 diffractometer.