tailieunhanh - Towards design of high spin metal-free materials

In this paper, in order to explore high-spin carbon-based magnetic materials with strong ferromagnetic coupling, geometric structure, electronic structure and magnetic properties of alternating stacks of π-radical-halogenated-hydrocarbons and diamagnetic molecules have been investigated based on density-functional theory with dispersion correction. | Communications in Physics, Vol. 23, No. 4 (2013), pp. 321-329 TOWARDS DESIGN OF HIGH SPIN METAL-FREE MATERIALS NGUYEN VAN THANH Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam NGUYEN ANH TUAN Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam and Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi, Ishikawa, 923-1292 Japan Received 19 Decmenber 2013 Accepted for publication 31 December 2013 Abstract. In this paper, in order to explore high-spin carbon-based magnetic materials with strong ferromagnetic coupling, geometric structure, electronic structure and magnetic properties of alternating stacks of π-radical-halogenated-hydrocarbons and diamagnetic molecules have been investigated based on density-functional theory with dispersion correction. These alternating stacks are predicted to avoid the typical antiferromagnetic spin-exchange of indentical face-to-face radicals via spin polarization of a diamagnetic molecule in between. Our results show that π-radicalhalogenated-hydrocarbons like perchlorophenalenyl (C13 Cl9 ) is strong ferromagnetic coupling if alternatingly stacked with aromatics like fluorinated coronene (C24 F12 ) or coronene (C24 H12 ), while fluorinated perinaphthenyl (C13 F9 ) and perinaphthenyl (C13 H9 ) are not an equally good choice. The role of ligand configuration in determining exchange coupling in stacks is discussed. These results would give some hints for designing new high-spin carbon-based ferromagnetic materials. I. INTRODUCTION Carbon is not only known as a biocompatible element, but also many advanced carbon-based materials with special functional and properties were synthesized, such as carbon nanotubes, fullerences, graphene. Moreover, in the past twenty years metal-free magnets made from carbon-based compounds have been discovered and, more recently, there have been reports on the observation of magnetism in carbon [1-9]. .