Title: Structural, Electronic and Magnetic Characteristics of Np2Co17
Authors: HALEVY ItzhakHEN AmirORION I.COLINEAU EricELOIRDI RachelGRIVEAU Jean-ChristopheGACZYNSKI PiotrWILHELM F.ROGALEV A.SANCHEZ J.-P.WINTERROSE M. L.MAGNANI NicolaSHIK ALEXANDERCACIUFFO Roberto
Citation: PHYSICAL REVIEW B vol. 85 no. 1 p. 014434
Publisher: AMER PHYSICAL SOC
Publication Year: 2012
JRC N°: JRC67903
ISSN: 1098-0121
URI: http://prb.aps.org/accepted/B/09072O13Y5515328300817f51411d4270dc8e201e
http://publications.jrc.ec.europa.eu/repository/handle/JRC67903
DOI: 10.1103/PhysRevB.85.014434
Type: Articles in Journals
Abstract: A previously unknown neptunium-transition-metal binary compound Np2Co17 has been synthesized and characterized by means of powder x-ray diffraction, 237Np Mössbauer spectroscopy, superconducting-quantuminterference-device magnetometry, and x-ray magnetic circular dichroism (XMCD). The compound crystallizes in a Th2Ni17-type hexagonal structure with room-temperature lattice parameters a = 8.3107(1) A° and c = 8.1058(1) A° . Magnetization curves indicate the occurrence of ferromagnetic order below TC > 350 K.Mössbauer spectra suggest a Np3+ oxidation state and give an ordered moment of μNp = 1.57(4) μB and μNp = 1.63(4) μB for the Np atoms located, respectively, at the 2b and 2d crystallographic positions of the P63/mmc space group. Combining these valueswith a sum-rule analysis of theXMCDspectra measured at the neptuniumM4,5 absorption edges, one obtains the spin and orbital contributions to the site-averaged Np moment [μS = −1.88(9) μB, μL = 3.48(9) μB]. The ratio between the expectation value of themagnetic-dipole moment and the spin magnetic moment (mmd/μS = +1.36) is positive as predicted for localized 5f electrons and lies between the values calculated in intermediate-coupling (IC) and jj approximations. The expectation value of the angular part of the spin-orbit-interaction operator is in excellent agreement with the IC estimate. The ordered moment averaged over the four inequivalent Co sites, as obtained from the saturation value of the magnetization, is μCo 1.6 μB. The experimental results are discussed against the predictions of first-principles electronic-structure calculations based on the spin-polarized local-spin-density approximation plus the Hubbard interaction.
JRC Institute:Institute for Transuranium Elements

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