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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Annealing control of hydrothermally grown hematite nanorods: Implication of structural changes and Cl concentration on weak ferromagnetism

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Carvalho-Jr, W. M. ; Mendonca-Ferreira, L. [1] ; Costa, F. N. [1] ; Ferreira, F. F. [1] ; Muche, D. N. F. [2, 3] ; Tofanello, R. A. [1] ; Castro, R. H. R. [2, 3] ; Souza, F. L. [2, 3, 1]
Total Authors: 8
[1] Carvalho-Jr, Jr., W. M., Univ Fed Abc, CCNH, BR-09210170 Santo Andre, SP - Brazil
[2] Univ Calif Davis, Dept Mat Sci & Engn, One Shields Ave, Davis, CA 95616 - USA
[3] Univ Calif Davis, NEAT ORU, One Shields Ave, Davis, CA 95616 - USA
Total Affiliations: 3
Document type: Journal article
Source: Journal of Alloys and Compounds; v. 799, p. 83-88, AUG 30 2019.
Web of Science Citations: 0

In-situ X-ray diffraction coupled with thermogravimetry and differential scanning calorimetry were used to elucidate the crystal phase transition from akaganeite to hematite nanorods. The results indicate that though complete phase transformation occurs at similar to 663 K, residual chlorines from the hydrothermal synthesis conditions strongly affect spin moment. The high temperature (>1023 K) shock-annealing reduced the chlorine concentration and consequent suppress most of surface defects on the rods. High temperature annealed hematite nanorods were then studied in terms of magnetic properties under different applied hydrostatic pressures and exhibited a shift of T-M to higher values, from 261 to 282 K with initial rate (partial derivative T-M/partial derivative P coefficient) of 46 K GPa(-1). Such positive dependence of T-M with hydrostatic applied pressure is consistent with several works reported in the literature investigating different morphologies in bulk and at nanoscale. In fact, gradual reduction of Cl species increases the spin mobility allowing the appearance of weak-ferromagnetism at room temperature. The crossover results strongly support the hypothesis that Cl dominates spin mobility. (C) 2019 Elsevier B.V. All rights reserved. (AU)

FAPESP's process: 16/02157-2 - Understanding the hematite nanostructured surface performing water adsorption microcalorimetry
Grantee:Flavio Leandro de Souza
Support type: Scholarships abroad - Research
FAPESP's process: 13/05471-1 - Effect of dopants in semiconductor nanostructures and their impact on photocatalytic performance
Grantee:Waldemir Moura de Carvalho Junior
Support type: Scholarships in Brazil - Doctorate
FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
Grantee:Elson Longo da Silva
Support type: Research Grants - Research, Innovation and Dissemination Centers - RIDC
FAPESP's process: 11/19924-2 - Study and development of advanced novel materials: electronic, magnetic and nanostructured: an interdisciplinary approach
Grantee:Carlos Rettori
Support type: Research Projects - Thematic Grants