Journal of Magnetism and Magnetic Materials 302 (2006) 294–296 Influence of spin reorientation on the magnetoelastic properties of NdFe 10.5 V 1.5 H. Khandan Fadafan a,Ã , M.R. Alinejad a , N. Tajabor a , D. Fruchart b,c , P. de Rango b,c , I. Popa b,c , D. Gignoux d a Department of Physics, Ferdowsi University of Mashhad, Mashhad 91775-1436, Iran b Laboratoire de Cristallographie, CNRS, BP 166, 38042 Grenoble cedex 9, France c CRETA, CNRS, BP 166, 38042 Grenoble cedex 9, France d Laboratoire Louis Ne´el, BP 166, 38042 CNRS, Grenoble cedex 9, France Received 25 July 2005 Available online 7 October 2005 Abstract The thermal expansion and magnetostriction of the NdFe 10.5 V 1.5 ferromagnetic compound were measured using the strain gauge technique, in temperatures ranging from 77 to 320 K and external field up to 1.5 T. Results show an anomalous dropdown of the thermal expansion coefficient corresponding well to the spin reorientation temperature of this compound T SR  133 K. The drop amplitude is reduced and its temperature width is broadened when applying magnetic field. The anisotropic and volume-forced magnetostriction exhibit, below 0.5 T, a well-pronounced maximum around T SR . It arises from the field-induced rotation of the magnetic moments which is maximum at T SR . r 2005 Elsevier B.V. All rights reserved. PACS: 75.30.m; 75.80.+q; 75.50.y; 65.40.de Keywords: Ferromagnetic; Thermal expansion; Magnetostriction; Magnetoelastic 1. Introduction The RE(Fe,M) 12 compounds (RE ¼ rare earth element, M ¼ V, Ti, Cr, Mo, Nb, W,y) are of interest because of their rather high Curie temperature and simple crystal structure. Simple crystal structure improves the rate of 1:12 phase formation, and also leads to a rather straightforward study of physical properties. These compounds crystallize in the tetragonal ThMn 12 -type structure, with space group I4/mmm. The RE atoms are located at the 2a sites while the Fe over three nonequivalent sites of 8i, 8j and 8f, the M (if 3d) atoms sharing the 8i site with Fe [1–3]. It was found that the Nd(Fe,V) 12 series reveal among the best intrinsic magnetic properties with high T C and saturation magne- tization [2]. In such compounds, the Nd(4f) sublattice exhibits in-plane magnetic anisotropy and the Fe(3d) sublattices contribute to uniaxial anisotropy. Due to their thermal variations, the different anisotropy terms make different contributions to the easy magnetic direction orientation, thus inducing to a spin reorientation transition from planar below T SR ¼ 133 K to axial at higher temperatures [1,3–5]. Interaction of magnetization with crystal lattice in 3d–4f compounds has been the subject of many experimental and theoretical analyses. In this respect, the Nd(Fe,V) 12 series has received less attention than the RE 2 Fe 17 and the RE 2 Fe 14 B ones [6]. Reference to the fair magnetic chara- cteristics of Nd(Fe,V) 12 (anisotropy field B A ¼ 0:93 T, saturation magnetization M S ¼ 1:03  10 6 A=m(m 0 M S ¼ 1:30 T) at room temperature), they may exhibit significant magnetoelastic effects under a weak enough applied field which is important both for practical and fundamental interests [2]. In the present study, the magnetoelastic effects ARTICLE IN PRESS www.elsevier.com/locate/jmmm 0304-8853/$ - see front matter r 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2005.09.021 Ã Corresponding author. Tel.: +98 511 840 5816; fax: +98 511 843 8032. E-mail address: ha_kh58@mail-stu.um.ac.ir (H. Khandan Fadafan).