Magnetic properties of Fe/Cu codoped ZnO nanocrystals

Ranjani Viswanatha, Doron Naveh, James R. Chelikowsky, Leeor Kronik, D. D. Sarma

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

Free-standing ZnO nanocrystals simultaneously doped with Fe and Cu with varying Fe/Cu compositions have been synthesized using colloidal methods with a mean size of ∼7.7 nm. Interestingly, while the Cu-doped ZnO nanocrystal remains diamagnetic and Fe-doped samples show antiferromagnetic interactions between Fe sites without any magnetic ordering down to the lowest temperature investigated, samples doped simultaneously with Fe and Cu show a qualitative departure in exhibiting ferromagnetic interactions, with suggestions of ferromagnetic order at low temperature. XAS measurements establish the presence of Fe 2+ and Fe 3+ ions, with the concentration of the trivalent species increasing in the presence of Cu doping, providing direct evidence of the Fe 2+ + Cu 2+ ⇌ Fe 3+ + Cu + redox couple being correlated with the ferromagnetic property. Using DFT, the unexpected ferromagnetic nature of these systems is explained in terms of a double exchange between Fe atoms, mediated by the Cu atom, in agreement with experimental observations.

Original languageEnglish
Pages (from-to)2009-2014
Number of pages6
JournalJournal of Physical Chemistry Letters
Volume3
Issue number15
DOIs
StatePublished - 2 Aug 2012
Externally publishedYes

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