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Рождественские лекции 2017 с 27 ноября, библиотека НИТУ МИСиС


	

Mechanisms of induced spin polarization of graphene and h-BN zig-zag nanoribbons on half-metallic La1-xSrxMnO3 supports

 

Pavel V. Avramov

 

       The structure of the interfaces and the mechanisms of induced spin polarization of infinite and finite narrow graphene- and h-BN zigzag nanoribbons placed on SrO- and MnO-terminated La1-xSrxMnO3 (001) surfaces were studied using Density Functional (DFT) electronic structure calculations. It was found that the nanoribbons are bounded with LSMO(001) surface by weak disperse interactions. The types of coordination of the fragments, the strength of bonding and the rate of spin polarization depend upon the nature of the fragments. Graphene nanoribbons are characterized by the lift of the spin degeneracy and strong spin-polarization caused by interface-induced structural asymmetry and oxygen-mediated indirect or direct exchange interactions with Mn ions of LSMO support. Spin polarization changes the semiconducting nature of infinite graphene nanoribbons to half-metallic state with visible spin-up density of states at the Fermi level. The asymmetry effect and exchange interactions cause spin polarization of h-BN nanoribbon as well with formation of embedded states inside the band gap. 


Exfoliation and reassembly route to layered nanocomposites for energy storage applications

 

Seung-Min Paek

 Department of Chemistry, Kyungpook National University, Daegu 41566, Republic of Korea

*E-mail: smpaek@knu.ac.kr

 

The exfoliation of various layered materials will be shown as representative examples with colloidal properties. The basal spacing of low dimensional solids can be increased by proper intercalation and/or ion-exchange reactions. The obtained exfoliated nanosheet can be used as “building blocks” to construct new ordered or disordered nanohybrid materials. Furthermore, the nanostructured hybrid materials could have increased porous properties, which eventually results in the enhanced electrochemical properties in secondary battery application. For example, nanostructured hybrid materials such as hollow spheres have been successfully fabricated via exfoliation and reassembling reaction of various layered materials such as layered titanate and ruthenate. The physicochemical properties of nanostructured hybrids, synthesized by utilizing chemical forces, could be optimized to have their enhanced applicability as electrodes in lithium and sodium ion batteries. Also, structural characterization of samples using X-ray absorption spectroscopy will be highlighted because the enhanced properties of hybrids are deeply correlated with the local structural variation of nanosized compounds.

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