98 research outputs found
Exchange Anisotropy in Epitaxial and Polycrystalline NiO/NiFe Bilayers
(001) oriented NiO/NiFe bilayers were grown on single crystal MgO (001)
substrates by ion beam sputtering in order to determine the effect that the
crystalline orientation of the NiO antiferromagnetic layer has on the
magnetization curve of the NiFe ferromagnetic layer. Simple models predict no
exchange anisotropy for the (001)-oriented surface, which in its bulk
termination is magnetically compensated. Nonetheless exchange anisotropy is
present in the epitaxial films, although it is approximately half as large as
in polycrystalline films that were grown simultaneously. Experiments show that
differences in exchange field and coercivity between polycrystalline and
epitaxial NiFe/NiO bilayers couples arise due to variations in induced surface
anisotropy and not from differences in the degree of compensation of the
terminating NiO plane. Implications of these observations for models of induced
exchange anisotropy in NiO/NiFe bilayer couples will be discussed.Comment: 23 pages in RevTex format, submitted to Phys Rev B
Hysteretic giant magnetoimpedance effect analyzed by first-order reversal curves
Hysteretic giant magnetoimpedance (GMI) of amorphous ribbons with a
well-defined transversal domain structure is investigated by means of
first-order reversal curves (FORC) analysis. The FORCs are not confined to the
hysteretic area, exceeding the major curve amplitude. Irreversible switches of
the transverse permeability, caused by domain wall structure transitions, may
be the origin of the observed FORC distribution. An interlinked
hysteron/anti-hysteron model is proposed to interpret it, which allows
analyzing the influence of frequency and magnetostriction upon the hysteretic
GMI effect.Comment: 19 pages, 9 figure
Study of the electrochemical behaviour of a 300 W PEM fuel cell stack by Electrochemical Impedance Spectroscopy
Electrochemical Impedance Spectroscopy (EIS) is a suitable and powerful diagnostic testing method for fuel cells because it is non-destructive and provides useful information about fuel cell performance and its components. In this work, EIS measurements were carried out on a 300 W stack with 20 elementary cells. Electrochemical impedance spectra were recorded either on each cell or on the stack. Parameters of a Randles-like equivalent circuit were fitted to the experimental data. In order to improve the quality of the fit, the classical Randles cell was extended by changing the standard plane capacitor into a constant phase element (CPE). The effects of output current, cell position, operating temperature and humidification temperature on the impedance spectra were studied.This work was supported by Generalitat Valenciana (PROMETEO/2010/023).PĂ©rez Page, M.; PĂ©rez Herranz, V. (2014). Study of the electrochemical behaviour of a 300 W PEM fuel cell stack by Electrochemical Impedance Spectroscopy. International Journal of Hydrogen Energy. 39(8):4009-4015. https://doi.org/10.1016/j.ijhydene.2013.05.121S4009401539
Domain Transformation and MI of Melt-extracted Co68.15Fe4.35Si12.25B13.25Nb1Cu1 Microwires by Cryogenic Joule Annealing
Permeability Characterization of Ferromagnetic Nanowires Arrays from Transmission-Line Measurements
Electrical impedance studies on a culture of a newly discovered strain of Streptomyces
NRC publication: Ye
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