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Title: Magnetic circular dichroism in Co1-xPtx nanowire bundles at the CoL2,3 edges

Abstract

Co1-xPtx nanowire arrays embedded in anodic aluminum oxidetemplates were fabricated by an electrochemical route. X-ray magneticcircular dichroism XMCD measurements were conducted at the Co L2,3 edgeson samples with an array of nanowire bundles at the substrate surfaces.The ratios between the orbital and the spin moments R were estimated tobe about 0.19+-0.03 and 0.07+-0.03 for 20 nm Co and 14 nm Co91Pt9nanowires, respectively. A strong temperature dependence of the R valuewas observed. The x-ray absorption spectra also indicated the presence ofCoO, which did not contribute to the XMCD signals.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
COLLABORATION - Joule Physics Laboratory,Institute for Materials Research, University of Salford, Salford M5 4WT,UK
OSTI Identifier:
932529
Report Number(s):
LBNL-63479
Journal ID: ISSN 0003-6951; APPLAB; TRN: US0803554
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 91; Journal Issue: 13; Related Information: Journal Publication Date: 09/24/2007
Country of Publication:
United States
Language:
English
Subject:
75; ABSORPTION SPECTRA; ALUMINIUM; MAGNETIC CIRCULAR DICHROISM; OXIDES; SPIN; SUBSTRATES; TEMPERATURE DEPENDENCE; advanced light source als

Citation Formats

Li, W., Zhang, J., Thompson, J., Shen, T.H., Arenholz, E., Morton, S.A., and Ellerby, M.. Magnetic circular dichroism in Co1-xPtx nanowire bundles at the CoL2,3 edges. United States: N. p., 2007. Web. doi:10.1063/1.2784186.
Li, W., Zhang, J., Thompson, J., Shen, T.H., Arenholz, E., Morton, S.A., & Ellerby, M.. Magnetic circular dichroism in Co1-xPtx nanowire bundles at the CoL2,3 edges. United States. doi:10.1063/1.2784186.
Li, W., Zhang, J., Thompson, J., Shen, T.H., Arenholz, E., Morton, S.A., and Ellerby, M.. Sat . "Magnetic circular dichroism in Co1-xPtx nanowire bundles at the CoL2,3 edges". United States. doi:10.1063/1.2784186.
@article{osti_932529,
title = {Magnetic circular dichroism in Co1-xPtx nanowire bundles at the CoL2,3 edges},
author = {Li, W. and Zhang, J. and Thompson, J. and Shen, T.H. and Arenholz, E. and Morton, S.A. and Ellerby, M.},
abstractNote = {Co1-xPtx nanowire arrays embedded in anodic aluminum oxidetemplates were fabricated by an electrochemical route. X-ray magneticcircular dichroism XMCD measurements were conducted at the Co L2,3 edgeson samples with an array of nanowire bundles at the substrate surfaces.The ratios between the orbital and the spin moments R were estimated tobe about 0.19+-0.03 and 0.07+-0.03 for 20 nm Co and 14 nm Co91Pt9nanowires, respectively. A strong temperature dependence of the R valuewas observed. The x-ray absorption spectra also indicated the presence ofCoO, which did not contribute to the XMCD signals.},
doi = {10.1063/1.2784186},
journal = {Applied Physics Letters},
number = 13,
volume = 91,
place = {United States},
year = {Sat Mar 10 00:00:00 EST 2007},
month = {Sat Mar 10 00:00:00 EST 2007}
}
  • We present an x-ray magnetic circular dichroism study performed at the U M{sub 4,5} edges on UFe{sub 2}, a ferromagnet with almost itinerant 5f electrons. The analysis of the branching ratio of the U M{sub 4,5} edges confirms the fact that the occupation number of the 5f states in UFe{sub 2} is lower than in other compounds where the f electrons are more localized. Magnetic circular dichroism effects are observed consistently with the presence of an orbital 5f magnetic moment which aligns parallel to the total magnetic moment. In agreement with a polarized neutron study, we find a nearly perfectmore » cancellation of the U-5f spin and orbital magnetic moments, which results in a vanishing small total U-5f magnetic moment. Results are discussed in comparison with atomic multiplet calculations. {copyright} {ital 1997} {ital The American Physical Society}« less
  • The soft-x-ray absorption and magnetic circular dichroism (MCD) cross sections at the {ital L}{sub 2} and {ital L}{sub 3} core-level edges of Ni and Fe have been calculated using a one-electron tight-binding band-structure approach. The tight-binding scheme is taken from the work of Papaconstantopoulos, supplemented with the inclusion of spin-orbit coupling in the {ital d} bands and fully relativistic dipole selection rules. In Ni, a fit to the various {ital L}{sub 2} and {ital L}{sub 3} intensity ratios can be achieved, but only with values of the {ital d}-band spin-orbit parameter {xi} and exchange parameter {Delta}{sub ex} at variance withmore » the ground-state band-structure values. For Fe, there is no plausible value of {xi} capable of explaining the intensity ratios; also, the predicted substructure within the {ital L}{sub 2} and {ital L}{sub 3} white lines is not seen in experiment. These failures of the one-electron approach are qualitatively consistent with expected many-body electronic rearrangements associated with core-hole creation. Some discussion is offered on sum rules and on orbital versus spin magnetic moments.« less
  • Magnetic circular dichroism (MCD) has been observed at the {ital L}{sub 2,3} absorption edges of ferromagnetic nickel by use of circularly-polarized soft-x-ray synchrotron radiation. The MCD intensity ratio between the {ital L}{sub 2} and {ital L}{sub 3} edges is found to differ appreciably from that predicted by a simple exchange-split-valence-band model. Fine MCD features, imperceptible in the absorption spectra, are also observed, and a tentative interpretation is given. This work, demonstrating the feasibility of MCD measurements in the soft-x-ray region, provides a new approach to study 3{ital d} and 4{ital f} ferromagnetic systems with their respective dipole-permitted 2{ital p}{r arrow}3{italmore » d} and 3{ital d}{r arrow}4{ital f} transitions.« less
  • The branching ratios in the circular dichroism of the rare-earth L{sub 23} edges are explained in a model where the 5d band is empty in the ground state. In the final state the 5d radial wave function contracts not only by the 5d-4f spin-spin interaction but by the complete exchange interaction. This explains the L{sub 3}/L{sub 2} ratios, the relative magnitude of the quadrupole contribution, and the dispersive shape of the signal in ionic compounds. {copyright} {ital 1997} {ital The American Physical Society}
  • Rabbit liver Zn metallothionein-(MT) will bind cadmium readily between -26 /sup 0/C and 70 /sup 0/C. The binding reaction was monitored by recording the circular dichroism and magnetic circular dichroism spectra, in the region of the RS/sup -/ ..-->.. Cd/sup 2 +/ charge transfer transition at 250 nm, at intervals as aliquots of cadmium were added. For all temperatures, these data can be analyzed in terms of a distributed mechanism for cadmium binding when Zn-MT is used, and a domain-specific mechanism when apo-MT is used. The CD spectrum measured at -26 /sup 0/C for Cd,Zn-MT, which was made by addingmore » excess cadmium directly to Zn/sub 7/-MT at -26 /sup 0/C, is not the same as the CD spectrum of Cd-MT prepared at room temperature from the same Zn/sub 7/-MT. Measurements of the stoichiometry of the cadmium and zinc bound to MT in the presence of excess cadmium at different temperatures indicates that below 5 /sup 0/C at least one zinc atom remains bound to the protein. The mixed metal metallothionein, Cd/Zn-MT, that always forms below 5 /sup 0/C, is characterized by a single maximum near 250 nm in the CD spectrum, rather than the derivative-shaped CD envelope that is diagnostic of the (Cd/sub 4/-S/sub 11/)/sup ..cap alpha../ cluster, which indicates that the zinc occupies a site in the ..cap alpha.. domain. Rearrangement of the bound metals to the domain-specific distribution takes place if Cd,Zn-MT, prepared at subzero temperatures, is warmed above 30 /sup 0/C.« less