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Interfacial dominated ferromagnetism in nanograined ZnO: a ?SR and DFT study.

ABSTRACT: Diamagnetic oxides can, under certain conditions, become ferromagnetic at room temperature and therefore are promising candidates for future material in spintronic devices. Contrary to early predictions, doping ZnO with uniformly distributed magnetic ions is not essential to obtain ferromagnetic samples. Instead, the nanostructure seems to play the key role, as room temperature ferromagnetism was also found in nanograined, undoped ZnO. However, the origin of room temperature ferromagnetism in primarily non-magnetic oxides like ZnO is still unexplained and a controversial subject within the scientific community. Using low energy muon spin relaxation in combination with SQUID and TEM techniques, we demonstrate that the magnetic volume fraction is strongly related to the sample volume fraction occupied by grain boundaries. With molecular dynamics and density functional theory we find ferromagnetic coupled electron states in ZnO grain boundaries. Our results provide evidence and a microscopic model for room temperature ferromagnetism in oxides.

SUBMITTER: Tietze T

PROVIDER: S-EPMC4352909 | biostudies-other | 2015

REPOSITORIES: biostudies-other

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Interfacial dominated ferromagnetism in nanograined ZnO: a μSR and DFT study.

Tietze Thomas T Audehm Patrick P Chen Yu-Chun YC Schütz Gisela G Straumal Boris B BB Protasova Svetlana G SG Mazilkin Andrey A AA Straumal Petr B PB Prokscha Thomas T Luetkens Hubertus H Salman Zaher Z Suter Andreas A Baretzky Brigitte B Fink Karin K Wenzel Wolfgang W Danilov Denis D Goering Eberhard E

Scientific reports 20150309

Diamagnetic oxides can, under certain conditions, become ferromagnetic at room temperature and therefore are promising candidates for future material in spintronic devices. Contrary to early predictions, doping ZnO with uniformly distributed magnetic ions is not essential to obtain ferromagnetic samples. Instead, the nanostructure seems to play the key role, as room temperature ferromagnetism was also found in nanograined, undoped ZnO. However, the origin of room temperature ferromagnetism in pr ...[more]

PMID: 25747456

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Project description:A comprehensive in vitro assessment of two commercial metal oxide nanoparticles, TiO2 and ZnO, was performed using human monocyte-derived macrophages (HMDM), monocyte-derived dendritic cells (MDDC), and T cell leukemia-derived cell line (Jurkat). TiO2 nanoparticles were found to be non-toxic whereas ZnO nanoparticles caused dose-dependent cell death. Subsequently, global gene expression profiling was performed to identify signaling pathways underlying the cytotoxicity caused by ZnO nanoparticles. Analysis was done with doses, 1ug/ml and 10ug/ml after 6 and 24 hours of exposure. Interestingly, 2703 genes were significantly differentially expressed in HMDM upon exposure to 10ug/ml ZnO nanoparticles, while in MDDCs only 12 genes were affected. In Jurkat cells, 980 genes were differentially expressed. It is noteworthy that the gene expression of metallothioneins was upregulated in all the three cell types. In addition to the common ZnO-inducible changes, a notable proportion of the genes were regulated in a cell type-specific manner. Using a panel of ZnO nanoparticles, we obtained an additional support that the cellular response to ZnO nanoparticles is caused by particle dissolution. Gene ontology analysis revealed that the top biological processes disturbed in HMDM and Jurkat cells were regulating cell death and growth. In addition, genes controlling immune system development were affected. Bioinformatics assessment showed that the top human disease category associated with ZnO-responsive genes in both HMDM and Jurkat cells was cancer. Overall, the study revealed novel genes and pathways for mediating ZnO nanoparticle-induced toxicity and demonstrated the value of assessing nanoparticle responses through combined transcriptomics and bioinformatics approach. Nanoparticles used in the study: ZnO-1 commercial (IBU-tec advanced materials AG), ZnO-2 (mandelic acid coated ZnO-1), ZnO-3 (mercaptopropyl-trimethoxysilane coated ZnO-1), ZnO-4 (methoxyl coated ZnO), ZnO-5 (diethylene glycol modified ZnO) and ZnO-9 (folic acid modified ZnO). Detailed particle production and characterization data can be found from the articles: Buerki-Thurnherr et al. 2012 Nanotoxicology and Tuomela et al.

Dataset Information

Interfacial dominated ferromagnetism in nanograined ZnO: a ?SR and DFT study.

Publications

Interfacial dominated ferromagnetism in nanograined ZnO: a μSR and DFT study.

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