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Title: Activation of High-TC Ferromagnetism in Co2+:TiO2 and Cr3+:TiO2 Nanorods and Nanocrystals by Grain Boundary Defects

Abstract

Colloidal Co2+- and Cr3+-doped TiO2 nanorods and nanocrystals were synthesized and studied by X-ray powder diffraction, electronic absorption spectroscopy, magnetic circular dichroism spectroscopy, magnetic susceptibility, and transmission electron microscopy. The nanorods were paramagnetic as colloids but showed room-temperature ferromagnetism when spin-coated aerobically into films. Crystalline domain size, thermal annealing, and dopant or defect migration are not the dominating factors converting the doped TiO2 nanocrystals from the paramagnetic state to the ferromagnetic state. The most important factor for activating ferromagnetism is found to be the creation of grain boundary defects, proposed to be oxygen vacancies at nanocrystal fusion interfaces. These defects are passivated and the ferromagnetism destroyed by further aerobic annealing. These results not only help elucidate the origins of the TMn+:TiO2 DMS ferromagnetism but also represent an advance toward the controlled manipulation of high-TC DMS ferromagnetism using external chemical perturbations.

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1006341
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society, 127(44):15568-15574; Journal Volume: 127; Journal Issue: 44
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; ANNEALING; COLLOIDS; DEFECTS; DIFFRACTION; FERROMAGNETISM; MAGNETIC CIRCULAR DICHROISM; MAGNETIC SUSCEPTIBILITY; OXYGEN; SPECTROSCOPY; TRANSMISSION ELECTRON MICROSCOPY; VACANCIES; Environmental Molecular Sciences Laboratory

Citation Formats

Bryan, J. D., Santangelo, Steven A., Keveren, Sean C., and Gamelin, Daniel R. Activation of High-TC Ferromagnetism in Co2+:TiO2 and Cr3+:TiO2 Nanorods and Nanocrystals by Grain Boundary Defects. United States: N. p., 2005. Web. doi:10.1021/ja0543447.
Bryan, J. D., Santangelo, Steven A., Keveren, Sean C., & Gamelin, Daniel R. Activation of High-TC Ferromagnetism in Co2+:TiO2 and Cr3+:TiO2 Nanorods and Nanocrystals by Grain Boundary Defects. United States. doi:10.1021/ja0543447.
Bryan, J. D., Santangelo, Steven A., Keveren, Sean C., and Gamelin, Daniel R. Wed . "Activation of High-TC Ferromagnetism in Co2+:TiO2 and Cr3+:TiO2 Nanorods and Nanocrystals by Grain Boundary Defects". United States. doi:10.1021/ja0543447.
@article{osti_1006341,
title = {Activation of High-TC Ferromagnetism in Co2+:TiO2 and Cr3+:TiO2 Nanorods and Nanocrystals by Grain Boundary Defects},
author = {Bryan, J. D. and Santangelo, Steven A. and Keveren, Sean C. and Gamelin, Daniel R.},
abstractNote = {Colloidal Co2+- and Cr3+-doped TiO2 nanorods and nanocrystals were synthesized and studied by X-ray powder diffraction, electronic absorption spectroscopy, magnetic circular dichroism spectroscopy, magnetic susceptibility, and transmission electron microscopy. The nanorods were paramagnetic as colloids but showed room-temperature ferromagnetism when spin-coated aerobically into films. Crystalline domain size, thermal annealing, and dopant or defect migration are not the dominating factors converting the doped TiO2 nanocrystals from the paramagnetic state to the ferromagnetic state. The most important factor for activating ferromagnetism is found to be the creation of grain boundary defects, proposed to be oxygen vacancies at nanocrystal fusion interfaces. These defects are passivated and the ferromagnetism destroyed by further aerobic annealing. These results not only help elucidate the origins of the TMn+:TiO2 DMS ferromagnetism but also represent an advance toward the controlled manipulation of high-TC DMS ferromagnetism using external chemical perturbations.},
doi = {10.1021/ja0543447},
journal = {Journal of the American Chemical Society, 127(44):15568-15574},
number = 44,
volume = 127,
place = {United States},
year = {Wed Nov 09 00:00:00 EST 2005},
month = {Wed Nov 09 00:00:00 EST 2005}
}
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