Enhanced ordering temperatures in antiferromagnetic manganite superlattices
|Title||Enhanced ordering temperatures in antiferromagnetic manganite superlattices|
|Publication Type||Journal Article|
|Year of Publication||2009|
|Authors||May 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 Title||Nature Materials|
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.
|URL||<Go to ISI>://000271050500019|