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Type: Artigo de periódico
Title: First order reversal curve analysis on NdFeB nanocomposite ribbons subjected to Joule heating treatments
Author: Pampillo, LG
Saccone, FD
Knobel, M
Sirkin, HRM
Abstract: Amorphous precursors with composition Nd4.5Fe72-xCo3+xCr2Al1B17.5 (x = 0, 2, 7, 12) were thermally treated by the Joule heating technique with a linearly varying electrical current. The crystallization kinetics was followed by monitoring the resistance of the ribbons during the heating up to the final applied current. Crystallized nanostructured phases coexist with an amorphous matrix, as it was observed by means of Mossbauer Spectroscopy and X-ray diffraction. The irreversible magnetic response of the Joule heated ribbons was analyzed by the First Order Reversal Curves (FORC) diagram technique. For the optimal treatments, associated with the higher maximum energy products for each sample composition, it was found that the main interaction is of a strongly dipolar characteristic. Over annealed samples show a FORC diagram that gives into account of softening, due to grain growth, for those phases precipitated at the first crystallization stage. When it is measured at 20 K, the hardest magnetic sample (Fe = 72 at.%, Co = 3 at.%, I-final = 0.5 A), exhibits a diagram with characteristics corresponding to dipolar interactions of soft phases. This fact is consistent with an enhancement of the exchange length due to the increase in the soft phase stiffness as it is expected at low temperatures. (c) 2012 Elsevier B.V. All rights reserved.
Subject: Composite materials
Nanostructured materials
Magnetic measurements
Country: Suíça
Editor: Elsevier Science Sa
Citation: Journal Of Alloys And Compounds. Elsevier Science Sa, v. 536, n. S389, n. S393, 2012.
Rights: fechado
Identifier DOI: 10.1016/j.jallcom.2012.01.104
Date Issue: 2012
Appears in Collections:Unicamp - Artigos e Outros Documentos

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