Long range antiferromagnetic order of formally non-magnetic Eu$^{3+}$ Van Vleck ions observed in multiferroic Eu$_{1-x}$Y$_{x}$MnO$_3$

TL;DR

This study demonstrates long-range antiferromagnetic order of Eu$^{3+}$ Van Vleck ions in multiferroic Eu$_{1-x}$Y$_{x}$MnO$_3$, induced by exchange coupling with Mn spins, revealing a new mechanism for magnetic ordering in non-magnetic ions.

Contribution

First observation of exchange-coupled long-range magnetic order of non-magnetic Eu$^{3+}$ ions in a multiferroic material, advancing understanding of magnetic interactions in such systems.

Findings

Eu$^{3+}$ ions exhibit antiferromagnetic order mirroring Mn magnetic structure

Exchange coupling induces magnetic order in formally non-magnetic ions

Potential for realizing exotic phases through exchange interactions in non-magnetic systems

Abstract

We report on resonant magnetic x-ray scattering and absorption spectroscopy studies of exchange-coupled antiferromagnetic ordering of Eu$^{3+}$ magnetic moments in multiferroic Eu$_{1-x}$Y$_{x}$MnO$_3$ in the absence of an external magnetic field. The observed resonant spectrum is characteristic of a magnetically ordered $^7F_1$ state that mirrors the Mn magnetic ordering, due to exchange coupling between the Eu $4f$ and Mn $3d$ spins. This is the first observation of long range magnetic order generated by exchange coupling of magnetic moments of formally non-magnetic Van Vleck ions, which is a step further towards the realization of exotic phases induced by exchange coupling in systems entirely composed of non-magnetic ions.