Magnetoelectric coupling and decoupling in multiferroic hexagonal YbFeO3 thin films

Abstract

The coupling between ferroelectric and magnetic orders is an enduring experimental challenge with fundamental importance to elucidate the nature of magnetoelectric (ME) effects in multiferroic materials. In this work, we have studied the response of magnetization to ferroelectric switching in thin-film hexagonal YbFeO3, an improper multiferroic which is a fruitful platform for investigating the ME coupling in single-phase materials. The bulk ME decoupling and potential domain-wall ME coupling were revealed using X-ray magnetic circular dichroism (XMCD) measurements with in-situ ferroelectric polarization switching. Our Landau theory analysis suggests that the bulk ME-coupled ferroelectric switching path has an higher energy barrier than that of the ME-decoupled path; this extra barrier energy is also too high to reduce by the magneto-static energy in the process of breaking single magnetic domains into multi-domains. In addition, the reduction of magnetization around the ferroelectric domain walls predicted by the Landau theory, may induce the domain-wall ME coupling in which he magnetization is correlated with the density of ferroelectric domain walls. These results provide important experimental evidences and theoretical insights to the rich possibilities of ME couplings in hexagonal ferrites.