التفاصيل البيبلوغرافية
| العنوان: |
Surface Ferromagnetism in Pr0.5Ca0.5MnO3Nanoparticles as a Consequence of Local Imbalance in Mn3+:Mn4+Ratio |
| المؤلفون: |
Aliyu, Haruna D., Alonso, Jose M., de la Presa, Patricia, Pottker, Walmir E., Ita, Benedict, Garcia-Hernández, Mar, Hernando, Antonio |
| المصدر: |
Chemistry of Materials; October 2018, Vol. 30 Issue: 20 p7138-7145, 8p |
| مستخلص: |
Half-doped praseodymium manganites, Pr0.5Ca0.5MnO3, synthesized by the sol–gel method produce highly crystalline nanoparticles with no structural disorder at the surface. As for most half-doped (Mn3+:Mn4+= 1) antiferromagnetic (AFM) charge-ordered manganites, ferromagnetism (FM) appears as particle size decreases. A possible origin of FM phase development is the lacking oxygen ligands at the surface that increases Mn3+at the expense of Mn4+in order to maintain electronic neutrality. In this work, we show that Mn3+:Mn4+= 1 ratio is preserved in the whole crystalline particle with the exception of the surface, where this ratio changes to Mn3+:Mn4+> 1. This Mn3+excess makes a double exchange Mn3+→ O2–→ Mn4+prevail over the superexchange, giving rise to the FM interactions. We show that a shell thickness of only one unit cell, with acell= 0.38 nm, is enough to explain the onset of FM at the surface, whereas the volume remains AFM. Furthermore, the FM to AFM ratio fits to the increase of surface-to-volume ratio with decreasing particle size. |
| قاعدة البيانات: |
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