Frustration induced inversion of magnetocaloric effect and enhanced cooling power in substituted Pyrochlore Iridates

TL;DR

This study explores how substituting Cr for Ir in pyrochlore iridates induces a cluster glass state, leading to a giant temperature window for magnetocaloric effects and significantly enhancing cooling power.

Contribution

It demonstrates that Cr substitution induces a cluster glass state and enhances both conventional and inverse magnetocaloric effects over a wide temperature range.

Findings

Induction of cluster glass transition in substituted iridates

Significant enhancement of magnetocaloric effects with substitution

Large cooling power over a broad temperature window

Abstract

We investigate the effect of partial replacement of extended 5d Ir4+ sites by localized 3d Cr3+ moments on the magnetocaloric properties of Y2Ir2O7 (YIO) pyrochlore iridates. We find that Y2Ir2-xCrxO7 (YICO) undergoes cluster glass transition, possibly due to RKKY like interaction between localized Cr3+ moments occupying random sites in the pyrochlore network, mediated by 5d Ir conduction electrons. The coexistence of ferromagnetic and antiferromagnetic clusters give rise to the conventional and inverse magnetocaloric effect (MCE). We observe significant enhancement of conventional as well as inverse MCE with substitution. Although the value of conventional MCE and inverse MCE in substituted Iridates are not large, the effect spans over a giant working temperature window, thus leading to orders of magnitude enhancement of cooling power, the value being comparable to standard magnetocalric materials.