Pressure-tuned magnetism and conductivity in pyrochlore iridates Lu₂Ir₂O₇ and Er₂Ir₂O₇

A₂Ir₂O₇iridates were proven to crystallise in the geometrically frustrated pyrochlore structure, which remains stable upon rare-earth cation substitution, temperature variation, and external pressure application. However, the change of interatomic distances and local distortions in the lattice frequently leads to complex electronic properties. The low-temperature behaviour in light-A iridates has been thoroughly investigated, including its evolution with pressure. The present pressure study reports the electrical transport and magnetotransport properties in heavy rare-earth Lu₂Ir₂O₇and Er₂Ir₂O₇. Both compounds reveal a semiconductor-insulator transition induced by the antiferromagnetic ordering of the all-in-all-out (AIAO) type in the Ir sublattice. The transition monotonously shifts to a higher temperature under applied pressure by approximately 20 K at 3 GPa. As the transition in resistivity originates in the antiferromagnetic order, the latter is expected to be enhanced with the applied pressure as well. Upon cooling the compound in a magnetic field, the AIAO/AOAI domain structure with non-zero net magnetic moment is formed, mirroring itself in an asymmetric term in the magnetoresistivity of Lu₂Ir₂O₇. The application of pressure then enhances the asymmetric term. The same behaviour is proposed for the whole heavy rare-earth A₂Ir₂O₇series (<i>A</i>= Gd-Lu), although with magnetoresistivity features masked significantly by a stronger response of magnetic<i>A</i>cations.