Magnetic charge injection in spin ice: a new way to fragmentation

TL;DR

This paper introduces a novel method to inject magnetic monopoles into spin ice using a staggered magnetic field, leading to a monopole crystal with magnetic fragmentation, demonstrated both theoretically and experimentally.

Contribution

It proposes and demonstrates a new mechanism for monopole injection in spin ice, resulting in a fragmented magnetic state with unique properties.

Findings

Monopole crystal stabilized in Ho$_2$Ir$_2$O$_7$

Magnetic fragmentation observed in the new state

Potential for tunable field-induced behaviors

Abstract

The complexity embedded in condensed matter fertilizes the discovery of new states of matter, enriched by ingredients like frustration. Illustrating examples in magnetic systems are Kitaev spin liquids, skyrmions phases, or spin ices. These unconventional ground states support exotic excitations, for example the magnetic charges in spin ices, also called monopoles. Beyond their discovery, an important challenge is to be able to control and manipulate them. Here, we propose a new mechanism to inject monopoles in a spin ice through a staggered magnetic field. We show theoretically, and demonstrate experimentally in the Ho$_2$Ir$_2$O$_7$ pyrochlore iridate, that it results in the stabilization of a monopole crystal, which exhibits magnetic fragmentation. In this new state of matter, the magnetic moment fragments into an ordered part and a persistently fluctuating one. Compared to conventional spin ices, the different nature of the excitations in this fragmented state opens the way to novel tunable field-induced and dynamical behaviors.