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Theoretical prediction of magnetism induced by defects or doping in non-metallic colloids has gained a renewed interests recently. In this work, we investigated the possible appearance of magnetism in Cu doped CaO nanocolloids activated by SPAN-80 in the framework of density functional theory (DFT). Despite of strong antiferromagnetic superexchange interaction between Cu2+ ions, the local magnetic moment of Cu may arise due to attachment of colloidal agent onto the surface of CaO nanocluster. The ferromagnetism attributes to the degeneration of Cu 3d orbitals in CaO crystal fields, the aspects of electron correlation and quantum spin fluctuation. | Communications in Physics, Vol. 25, No. 4 (2015), pp. 359-365 DOI:10.15625/0868-3166/25/4/0 STRONG ELECTRON CORRELATION IN CU-DOPED CAO NANOCOLLOID NGUYEN THUY TRANG Faculty of Physics, Hanoi University of Science, Vietnam National University, Hanoi HOANG NAM NHAT Faculty of Engineering Physics and Nano Technology, University of Engineering and Technology, Vietnam National University, Hanoi E-mail: nhathn@vnu.edu.vn Received 29 November 2015 Accepted for publication 24 December 2015 Abstract. Theoretical prediction of magnetism induced by defects or doping in non-metallic colloids has gained a renewed interests recently. In this work, we investigated the possible appearance of magnetism in Cu doped CaO nanocolloids activated by SPAN-80 in the framework of density functional theory (DFT). Despite of strong antiferromagnetic superexchange interaction between Cu2+ ions, the local magnetic moment of Cu may arise due to attachment of colloidal agent onto the surface of CaO nanocluster. The ferromagnetism attributes to the degeneration of Cu 3d orbitals in CaO crystal fields, the aspects of electron correlation and quantum spin fluctuation. Keywords: DFT, band-gap, CaO, calcium-oxide, mBJ, PBE, functional. I. INTRODUCTION Owing to the wide scope of application from optoelectronics to biology the rock salt compounds continuously attract the growing interests of scientists worldwide. A defect induced photoemission in CaO was a subject of many researches [1] and this popular rock salt proposed itself as a brilliant candidate for application in laser windows, IR domes, IR optical fiber. . . Recently, there has been a renewed interest in CaO due to a possibility of magnetism in doped (non-metallic) CaO and defect-induced metallic CaO compounds [2–5]. On the basis of tight-binding-like model, I. S. Elfimov et al. [2] showed that the cation vacancies in the divalent monoxides with rock salt structure as well as in any other compounds with octahedral coordination might .
