Enhanced ordering temperatures in antiferromagnetic manganite superlattices

TitleEnhanced ordering temperatures in antiferromagnetic manganite superlattices
Publication TypeJournal Article
Year of Publication2009
AuthorsMay SJ, Ryan PJ, Robertson JL, Kim JW, Santos TS, Karapetrova E, Zarestky JL, Zhai X, te Velthuis SGE, Eckstein JN, Bader SD, Bhattacharya A
Journal TitleNature Materials
Date Published11/01
ISBN Number1476-1122
Accession NumberISI:000271050500019
Keywordsfilms, growth

The disorder inherent to doping by cation substitution in the complex oxides can have profound effects on collective-ordered states. Here, we demonstrate that cation-site ordering achieved through digital-synthesis techniques can dramatically enhance the antiferromagnetic ordering temperatures of manganite films. Cation-ordered (LaMnO3)(m)/(SrMnO3)(2m) superlattices show ;eel temperatures (T-N) that are the highest of any La1-xSrxMnO3 compound, similar to 70 K greater than compositionally equivalent randomly doped La1/3Sr2/3MnO3. The antiferromagnetic order is A-type, consisting of in-plane double-exchange-mediated ferromagnetic sheets coupled antiferromagnetically along the out-of-plane direction. Through synchrotron X-ray scattering, we have discovered an in-plane structural modulation that reduces the charge itinerancy and hence the ordering temperature within the ferromagnetic sheets, thereby limiting T-N. This modulation is mitigated and driven to long wavelengths by cation ordering, enabling the higher T-N values of the superlattices. These results provide insight into how cation-site ordering can enhance cooperative behaviour in oxides through subtle structural phenomena.

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