# Robust pinning of magnetic moments in pyrochlore iridates

## TL;DR

This paper investigates a unique magnetic phenomenon in pyrochlore iridates, where non-magnetic Ir defects induce ferromagnetic droplets and a hysteresis loop shift, explained by an exchange-bias-like effect involving complex magnetic interactions.

## Contribution

It introduces a model explaining the cooling-field induced hysteresis shift in pyrochlore iridates with Ir defects, highlighting the role of exchange interactions and magnetic octupolar order.

## Key findings

- Hysteresis loop shifts are observed in pyrochlore iridates with Ir defects.
- The shift is explained by ferromagnetic droplets pinned by the AIAO antiferromagnetic background.
- The magnetic pinning remains stable up to 35 T, indicating robust magnetic order.

## Abstract

Pyrochlore iridates A2Ir2O7 (A = rare earth elements, Y or Bi) hold great promise for realizing novel electronic and magnetic states owing to the interplay of spin-orbit coupling, electron correlation and geometrical frustration. A prominent example is the formation of all-in/all-out (AIAO)antiferromagnetic order in the Ir4+ sublattice that comprises of corner-sharing tetrahedra. Here we report on an unusual magnetic phenomenon, namely a cooling-field induced shift of magnetic hysteresis loop along magnetization axis, and its possible origin in pyrochlore iridates with non-magnetic Ir defects (e.g. Ir3+). In a simple model, we attribute the magnetic hysteresis loop to the formation of ferromagnetic droplets in the AIAO antiferromagnetic background. The weak ferromagnetism originates from canted antiferromagnetic order of the Ir4+ moments surrounding each non-magnetic Ir defect. The shift of hysteresis loop can be understood quantitatively based on an exchange-bias like effect in which the moments at the shell of the FM droplets are pinned by the AIAO AFM background via mainly the Heisenberg (J) and Dzyaloshinsky-Moriya (D) interactions. The magnetic pinning is stable and robust against the sweeping cycle and sweeping field up to 35 T, which is possibly related to the magnetic octupolar nature of the AIAO order.