Title: Antiferromagnetism in UO2 Thin Epitaxial Films
Authors: BAO ZhaouiSPRINGELL RossWALKER H.c.LEISTE H.KUEBEL ChristianPRANG R.NISBET GarethLANGRIDGE S.WARD R.c.c.GOUDER ThomasCACIUFFO RobertoLANDER G.h.
Citation: PHYSICAL REVIEW B vol. 88 no. 13 p. 134426
Publisher: AMER PHYSICAL SOC
Publication Year: 2013
JRC N°: JRC84372
ISSN: 1098-0121
URI: http://prb.aps.org/abstract/PRB/v88/i13/e134426
http://publications.jrc.ec.europa.eu/repository/handle/JRC84372
DOI: 10.1103/PhysRevB.88.134426
Type: Articles in periodicals and books
Abstract: Thin films (250–4500 A° ) of epitaxial UO2 were produced by reactive sputtering on two different substrate materials: LaAlO3 and CaF2. Using the large enhancement present with resonant x-ray scattering using photons at the uraniumM4 absorption edge, antiferromagnetic (AF) order was found in all films. The ordering temperature T N is the same as the bulk, but the films show second-order (continuous) transitions in contrast to the first-order bulk transition. For LaAlO3-based films, an additional strong diffuse magnetic disorder is observed, which is reminiscent of the second-length scale, associated with structural disorder and/or strain. By using a formulation accounting for the strong absorption and coherent nature of the photons, the energy widths at the UM4 resonances can be related to the thickness of the AF region. The LaAlO3-based films do not order magnetically over more than ∼600 A° , whereas the CaF2-based film orders throughout. Further, for thicker films (>1000 A° ) the fitting procedure shows that the AF order is located at the top of the LaAlO3-based film. This points to the formation in thicker films of a nonmagnetic layer of UO2 adjacent to the substrate, which may have tetragonal symmetry.
JRC Directorate:Nuclear Safety and Security

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