Influence of the small substitution of Z=Ni, Cu, Cr, V for Fe on the magnetic, magnetocaloric, and magnetoelastic properties of LaFe 11.4 Si 1.6 Arjun K. Pathak a,n , Prakash Basnyat a , Igor Dubenko a , Shane Stadler b , Naushad Ali a a Department of Physics, Southern Illinois University Carbondale, 1245 Lincoln Dr., Carbondale, IL 62901, USA b Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA article info Article history: Received 2 June 2009 Received in revised form 23 October 2009 Available online 31 October 2009 Keywords: Magnetocaloric Magnetostriction Strain abstract We have studied the magnetic, magnetocaloric, and magnetostriction properties of LaFe 11.4 Si 1.6 and La(Fe 0.99 Z 0.01 ) 11.4 Si 1.6 (Z=Ni, Cu, Cr, V) compounds using magnetization and strain gauge techniques. It was found that substitution of 1% of the Fe by Z-elements results in an increase in the Curie temperature (T C ), and affects the magnetostriction and magnetocaloric properties of the parent compound, LaFe 11.4 Si 1.6 . A maximum shift in T C of about 11 K, and significantly smaller hysteresis losses in the vicinity of T C compared with those of the base compound, were found for Z=V. The maximum magnetovolume coupling constant was estimated to be n dd E2.7  10 3 (m B /Fe atom) 2 for the parent compound. The changes in the volume magnetostriction, the magnetovolume coupling constant, and the magnetocaloric properties are strongly correlated with composition. The relative effects of the variation in cell parameters and electron concentration on the magnetostriction, T C , and the magnetocaloric properties are discussed. & 2009 Elsevier B.V. All rights reserved. 1. Introduction Recently, some metallic ferromagnetic materials have drawn considerable attention due to their giant magnetocaloric effects (MCE) and magnetostriction properties and, consequently, for their possible application in magnetic refrigeration and magne- tomechanical devices, such as transducers [1–4]. The intermetallic compounds LaFe 13 x Si x crystallize in a NaZn 13 -type cubic structure with eight formula units (f.u.) per crystal cell. The binary LaFe 13 compound does not exist due to a positive heat of formation between La and Fe, however, this type of compound can be stabilized by addition of a third element. Hypothetically, the Fe atoms in LaFe 13 would be located at two different crystal sites: Fe1 at the Wyckoff position 8b (0, 0, 0) and Fe2 at 96i (0, y, z) in a ratio of 1:12 [5]. The La atom is located at 8a (1/4, 1/4, 1/4) and is surrounded by 24 Fe2 atoms. The Si atoms in LaFe 13 x Si x randomly occupy both 8b and 96i sites. It was shown that the Fe1–Fe2 distance can play an important role in the exchange interaction and thereby affect the T C of LaFe 13x Si x [5,6]. The outer shell electrons are hybridized in metallic compounds, giving rise to a conduction electron band. Therefore, there are two major factors that can affect the magnetic properties of LaFe 13x Si x as a result of composition changes: these are the change in interatomic distance and the change in the density of d-electron states at the Fermi level. It was reported that compounds with low concentrations of Si in LaFe 13x Si x undergo a first order phase transition (FOPT) from a ferromagnetic (FM) to a paramagnetic (PM) state at T C , and a field- induced itinerant-electron metamagnetic transition (IEM) from a PM to FM phase [7–10]. It was also shown that the substitution of Fe by Si in LaFe 13 x Si x increases T C and, for the x = 1.6 compound, a FOPT from a FM to PM state was observed at T C E208 K [10]. It is well known that the properties of itinerant metamagnets are extremely sensitive to the density of the 3d-electrons at the Fermi level. Therefore, a strong influence of the d-electron concentration on the magnetic, magnetocaloric, and magnetoe- lastic properties can be expected with the substitution of Z-elements in the La(Fe,Z) 11.4 Si 1.6 system. In this paper, we present a study of the influence of the changes in the 3d-electron concentration resulting from the substitution of small amounts (1%) of Fe by Ni, Cu, Cr, and V metals on the magnetic, magnetocaloric, and magnetoelastic properties of LaFe 11.4 Si 1.6 . It was found that for all substituents, Z, a change in Fe content strongly affects T C , magnetic entropy changes (DS M ), refrigeration capacity (RC), and magnetostriction. The results are discussed considering the relative effects of the variation in the average atomic radius and electron concentration on the properties of La(Fe 1 x Z x ) 11.4 Si 1.6 . 2. Experimental techniques Approximately, 4 g polycrystalline buttons of La(Fe 1 x Z x ) 11.4 Si 1.6 (x =0; x =0.01 and Z=Ni, Cu, Cr, V) were fabricated by ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials 0304-8853/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2009.10.043 n Corresponding author. Fax: + 1 618 453 1056. E-mail address: pathak@siu.edu (A.K. Pathak). Journal of Magnetism and Magnetic Materials 322 (2010) 692–697