Photo-induced Antiferromagnetic-ferromagnetic Transition and Electronic Structure Modulation in GdBaCo$_2$O$_{5.5}$ Thin Film

TL;DR

This study explores ultrafast magnetic phase transitions and electronic structure changes in GdBaCo$_2$O$_{5.5}$ thin films induced by light, revealing a photo-induced AFM-FM transition and associated spin state modifications.

Contribution

It demonstrates the first observation of a photo-induced antiferromagnetic to ferromagnetic transition in this material using time-resolved x-ray techniques.

Findings

Photo-induced AFM-FM transition observed.

Transient XMCDR exceeds unpumped value.

Concomitant spin state transition inferred.

Abstract

We investigate both the ferromagnetic (FM) and antiferromagnetic (AFM) ultrafast dynamics of a strongly correlated oxide system, GdBaCo$_2$O$_{5.5}$ thin film, by time-resolved x-ray magnetic circular dichroism in reflectivity (XMCDR) and resonant magnetic x-ray diffraction (RMXD). A photo-induced AFM-FM transition characterized by an increase of the transient XMCDR beyond the unpumped value and a decay of RMXD was observed. The photon-energy dependence of the transient XMCDR and reflectivity can likely be interpreted as a concomitant photo-induced spinstate transition.