Enhanced ordering temperatures in antiferromagnetic manganite superlattices.
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 (LaMnO{sub 3}){sub m}/(SrMnO{sub 3}){sub 2m} superlattices show Neel temperatures (TN) that are the highest of any La{sub 1-x}Sr{sub x}MnO{sub 3} compound, {approx}70 K greater than compositionally equivalent randomly doped La{sub 1/3}Sr{sub 2/3}MnO{sub 3}. 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 TN. This modulation is mitigated and driven to long wavelengths by cation ordering, enabling the higher TN values of the superlattices. These results provide insight into how cation-site ordering can enhance cooperative behavior in oxides through subtle structural phenomena.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 979882
- Report Number(s):
- ANL/MSD/JA-65468
- Journal Information:
- Nature Mater., Journal Name: Nature Mater. Journal Issue: 11 ; 2009 Vol. 8
- Country of Publication:
- United States
- Language:
- ENGLISH
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