Anisotropic Magnetic Resonance in Random Nanocrystal Quantum Dot Ensembles

António J.S. Almeida, Ayaskanta Sahu, David J. Norris, Gleb N. Kakazei, Haripriya Kannan, Martin S. Brandt, Martin Stutzmann, Rui N. Pereira*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Magnetic anisotropy critically determines the utility of magnetic nanocrystals (NCs) in new nanomagnetism technologies. Using angular-dependent electron magnetic resonance (EMR), we observe magnetic anisotropy in isotropically arranged NCs of a nonmagnetic material. We show that the shape of the EMR angular variation can be well described by a simple model that considers magnetic dipole-dipole interactions between dipoles randomly located in the NCs, most likely due to surface dangling bonds. The magnetic anisotropy results from the fact that the energy term arising from the magnetic dipole-dipole interactions between all magnetic moments in the system is dominated by only a few dipole pairs, which always have an anisotropic geometric arrangement. Our work shows that magnetic anisotropy may be a general feature of NC systems containing randomly distributed magnetic dipoles.

Original languageEnglish
Pages (from-to)11333-11341
Number of pages9
JournalACS Omega
Volume5
Issue number20
DOIs
Publication statusPublished - 26 May 2020

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