The effect of Gd doping in La 1xy Gd x Sr y MnO 3 compound on nanocrystalline structure by X-ray Absorption Spectroscopy (XAS) technique Sujittra Daengsakul a , Pinit Kidkhunthod b,⇑ , Orapan Soisang a , Tanya Kuenoon a , Atipong Bootchanont c , Santi Maensiri c a Physics Department, Faculty of Science, Khon Kaen University, Muang District, Khon Kaen 40002, Thailand b Synchrotron Light Research Institute (Public Organization), 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand c School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand article info Article history: Received 15 October 2014 Received in revised form 17 January 2015 Accepted 30 March 2015 Available online 4 April 2015 Keywords: LGSM nanocrystalline powders Manganite compounds X-ray Absorption Spectroscopy abstract This work presents the structural study of La 1xy Gd x Sr y MnO 3 or LGSM compositions where 0 6 x 6 0.15 and 0 6 y 6 0.45, respectively. In particular, the effect of doping Gd concentration and the size mismatch of A-site cations from the substitution of Gd for La on the MnO 6 octahedral structure is focused as the average size of the cations occupying in A-site is fixed. The LGSM nanoparticles are carefully studied and analyzed using X-ray diffraction (XRD) and X-ray Absorption Spectroscopy (XAS) including X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS). The XRD results obtained from Rietveld refinement show that all nano-powder samples have rhombohedral structure. From the XANES technique we found that the effect of Gd substitutions causes the slight increase of mean oxidation state of Mn from 3.50 to 3.65. Furthermore, the results of MnO 6 octahedral analysis obtained from EXAFS technique show that the local structure around Mn atoms for LG05 and LG10 samples can be explained by 4(s) + 2(l) model while the LG15 sample can be explained by 6 model. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Owing to a discovery of colossal magnetoresistance (CMR) phe- nomenon [1–3], a great attention has focused on applications of CMR materials such as in magnetic reader and record storage sys- tems and sensors [4]. Moreover, their applications can be used as contrast agents in magnetic resonance imaging (MRI) [5]. One of interesting CMR materials which is widely studied is manganite perovskite compound [3]. Typically, manganite perovskite com- pounds have structural formula as A 1x B x MnO 3 where A is a triva- lent lanthanide cation, e.g., La, Ln, Pr and B is a divalent cation, e.g., alkaline earth elements. When some trivalent La 3+ ions are substi- tuted by divalent cations such as Sr 2+ a compound of La 1x Sr x MnO 3 (LSMO) will be obtained. This substitution causes a creation of holes (hole-doping) that induces a mixed valences state of Mn ions (Mn 3+ /Mn 4+ ) leading to enhancement of the magnetic transition temperature, and the presence of the ferromagnetism and conduc- tivity in this compound [6,7]. Zener [8] proposed a framework of Zener’s double exchange (DB) model involving the coupling of Mn 3+ and Mn 4+ ions in order to explain a change in electrical and magnetic properties of these materials. The important parameters that effect these properties descripted by the DB model are the hole concentration which is provided by the amount of Mn 4+ ion, and the overlapping of the Mn 3d orbitals and O 2p orbitals depending on the distance and bond angle between Mn and O ions (d Mn–O and h Mn–O–Mn ) in MnO 6 octahedra [9]. In order to understanding the displayed properties, several research have been attempted to study about these materials con- sisting the parameters of the Mn 4+ content, average size of the cations occupying in A-site or hr A i and the mismatch effect factor or r 2 due to disordering of ionic size in A-site for manganite compound on their physical properties [9–12]. Most of them demonstrated consistently that the Mn 4+ , hr A i and r 2 have a large effect on structure, magnetic and CMR properties. Daengsakul et al. [13] also presented the average Mn oxidation state (refer to the Mn 4+ concentration) change with variation of hr A i for LSMO and LAMO (A = Ca, Ba, Na) compositions. They found that the mag- netization, M, increase with increasing of hr A i showing the highest M values at hr A i 1.24 Å. This behavior is good agreement with the variation of Curie temperature, T C , with hr A i showing the highest T C at hr A i 1.23–1.26 Å for the Ln 1x A x MnO 3 series reported by http://dx.doi.org/10.1016/j.mee.2015.03.065 0167-9317/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: pinit@slri.or.th (P. Kidkhunthod). Microelectronic Engineering 146 (2015) 38–42 Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee