The influence of Cr-composition on the local magnetic structure of FeCr alloys A. Idhil a , C.N. Borca a,⇑ , A.-C. Uldry a , N. Zema b , S. Turchini b , D. Catone b , A. Foelske a , D. Grolimund a , M. Samaras c,d a Paul Scherrer Institute, Villigen-PSI 5232, Switzerland b CNR, Istituto di Struttura della Materia, Via del fosso del cavaliere 100, Roma 00133, Italy c University of Stuttgart, Stuttgart 70550, Germany d University of Applied Science, Rapperswil 8640, Switzerland article info Article history: Available online 16 September 2011 Keywords: FeCr alloy XMCD Spin magnetic moment Orbital magnetic moment abstract Element specific investigations using X-ray magnetic circular dichroism (XMCD) were performed on FeCr alloys for Cr concentrations ranging from 6 to 16 at.% Cr. Measurements at the Fe L edge show a scattered distribution of the spin and orbital magnetic moments which is not observed for the global bulk magnetic moment. The Cr is aligned ferromagnetic up to 16 at.% Cr and in opposite direction with respect to the Fe magnetic moments. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction The FeCr alloys are considered as candidate materials for struc- tural components in advance fission reactor and future fusion power reactors, due to their superior properties of increased strength and hardness, low oxidation rate, corrosion resistance and retention of strength at high temperatures. Magnetism is inherently present in the FeCr alloy and has until recently been ne- glected when assessing mechanical properties and lifetime of these materials exposed to extreme conditions. Ab initio calculations have shown that magnetism affects the stability configuration and mobility of defects present in pure Fe [1]. Addition of antifer- romagnetic Cr in the ferromagnetic Fe matrix leads to interesting magnetic configurations in the FeCr alloy phase diagram [2]. Using ab initio calculations, an anomaly in the formation energy of the FeCr alloy has been reported [3]. The authors found a negative value of formation energy at low Cr concentrations, which turns positive at higher Cr concentrations. Klaver et al. [4] showed that Cr–Cr repulsion promoted by magnetic frustration is significant up to the sixth nearest neighbors and very strong for the first near- est neighbors. Recent X-ray magnetic circular dichroism (XMCD) and ex- tended X-ray absorption fine structure (EXAFS) measurements as well as ab initio calculations on Fe-6.2 at.% Cr and Fe-12.7 at.% Cr have furthermore indicated the correlation existent between mag- netism and structure in this transition metal alloy [5]. We intend to complement the previous work using a more complete approach which includes further EXAFS and XMCD measurements on high purity samples, as well as density functional theory (DFT) calcula- tions for several concentrations ranging between 5 and 16 at.% Cr. In this work we report on the XMCD measurements at room tem- perature for both Fe and Cr L-edges. Both Fe and Cr elemental mo- ments existent in magnetically saturated specimens are investigated and compared to the measured as well as calculated global magnetic moments. We find that the Fe spin magnetic mo- ments show a scattered distribution, which is not observed for the total bulk magnetic moment. 2. Materials and methods FeCr materials have been prepared by arc-melting pure Fe and Cr under Ar atmosphere. The details about material preparation can be found in Ref. [5]. We have studied FeCr alloys with Cr -concentrations up to 16 at.%, as well as a high-purity Fe sample, as a reference material. The specimens were prepared as thin plates of about 4  4 mm 2 , with 0.5 mm thickness, with mechani- cally polished mirror like surfaces. The XPS data were obtained with an ESCALAB 220iXL (Thermo Scientific, USA, formerly V.G. Scientific) equipment, using Al K a (1486.6 eV) radiation. The specimens were cleaned by ultra-high vacuum argon sputtering operated at 3 kV, at a rate of 1 nm/min. The photoelectron spectra have been recorded at normal emission angle as a function of sputtering time, up to 900 s. The X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (MCD) experiments were performed on the Circular Polarization Beamline at Elettra Synchrotron Radiation Facility in Trieste, Italy. Absorption spectra were acquired, at room 0168-583X/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2011.08.071 ⇑ Corresponding author. E-mail address: camelia.borca@psi.ch (C.N. Borca). Nuclear Instruments and Methods in Physics Research B 284 (2012) 1–5 Contents lists available at SciVerse ScienceDirect Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb