Pressure-tuned magnetism and conductivity in pyrochlore iridates Lu₂Ir₂O₇and Er₂Ir₂O₇

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Chemistry

Background:

• A2Ir2O7 iridates crystallize in geometrically frustrated pyrochlore structures, exhibiting complex electronic properties due to lattice distortions.
• While light rare-earth iridates' low-temperature behavior under pressure is known, heavy rare-earth analogs require further investigation.

Purpose of the Study:

• To investigate the electrical transport and magnetotransport properties of heavy rare-earth iridates, specifically Lu2Ir2O7 and Er2Ir2O7, under applied pressure.
• To understand the influence of pressure on the semiconductor-insulator transition and its relation to antiferromagnetic ordering.

Main Methods:

• Experimental measurement of electrical transport and magnetotransport properties.
• Application of external pressure (up to 3 GPa) to study material response.
• Analysis of the relationship between magnetic ordering and electronic transitions.

Main Results:

• Both Lu2Ir2O7 and Er2Ir2O7 exhibit a semiconductor-insulator transition linked to antiferromagnetic ordering of the all-in-all-out (AIAO) type in the Ir sublattice.
• Applied pressure shifts this transition to higher temperatures (approx. 20 K at 3 GPa) and is expected to enhance antiferromagnetic order.
• An asymmetric term in magnetoresistivity, linked to AIAO/AOAI domain structures, is observed in Lu2Ir2O7 and enhanced by pressure.

Conclusions:

• Pressure plays a significant role in tuning the electronic and magnetic properties of heavy rare-earth iridates.
• The observed phenomena are proposed to be characteristic of the entire heavy rare-earth A2Ir2O7 series, though potentially masked by magnetic rare-earth cations.
• Understanding these pressure-induced effects is crucial for exploring potential applications of pyrochlore iridates.