Probing photo-induced melting of antiferromagnetic order in La0.5Sr1.5MnO4 by ultrafast resonant soft X-ray diffraction

TL;DR

This study uses ultrafast resonant soft X-ray diffraction to investigate how light induces rapid changes in spin and orbital orders in La0.5Sr1.5MnO4, revealing nonthermal coupling effects in phase transitions.

Contribution

It demonstrates the ability to separately probe spin and orbital dynamics during photo-induced phase transitions in complex oxides.

Findings

Ultrafast melting of antiferromagnetic spin order observed.

Orbital order is only partially affected by photo-excitation.

Cluster calculations support interpretation of magnetic state changes.

Abstract

Photo-excitation in complex oxides1 transfers charge across semicovalent bonds, drastically perturbing spin and orbital orders2. Light may then be used in compounds like magnetoresistive manganites to control magnetism on nanometre lengthscales and ultrafast timescales. Here, we show how ultrafast resonant soft x-ray diffraction can separately probe the photo-induced dynamics of spin and orbital orders in La0.5Sr1.5MnO4. Ultrafast melting of CE antiferromagnetic spin order is evidenced by the disappearance of a (1/4,1/4,1/2) diffraction peak. On the other hand the (1/4,1/4,0) peak, reflecting orbital order, is only partially reduced. Cluster calculations aid our interpretation by considering different magnetically ordered states accessible after photo-excitation. Nonthermal coupling between light and magnetism emerges as a primary aspect of photo-induced phase transitions in manganites.