Use of conventional electrochemical techniques to produce crystalline FeRh alloys induced by Ag seed layer R.D. Noce a,⇑ , A.V. Benedetti a , E.C. Passamani b , H. Kumar c , D.R. Cornejo c , M. Magnani d a Instituto de Química, Universidade Estadual Paulista, UNESP, 14800-900 Araraquara, SP, Brazil b Departamento de Física, Universidade Federal do Espírito Santo, 29075-910 Vitória, ES, Brazil c Instituto de Física, Universidade de São Paulo, USP, 05508-090 São Paulo, SP, Brazil d Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), 13083-970 Campinas, SP, Brazil article info Article history: Received 5 February 2013 Received in revised form 23 March 2013 Accepted 29 March 2013 Available online 8 April 2013 Keywords: FeRh alloys Ag seed layer Galvanic displacement Electrodeposition abstract By combining galvanic displacement and electrodeposition techniques, an ordered Fe 20 Rh 80 structure deposited onto brass was investigated by X-ray diffractometry, Mössbauer spectroscopy and magnetiza- tion measurements. Mössbauer and X-ray diffraction analyses suggest that the Fe–Rh alloy directly elec- trodeposited onto brass displays a nanocrystalline state while a similar alloy deposited onto Ag/brass shows a faced centered cubic-like structure, with dendrites-like features. These results directly indicate that the presence of Ag seed layer is responsible for the Fe–Rh alloy crystallization process. In addition, room temperature Mössbauer data indicate firstly paramagnetic states for two Fe-species. In the domi- nant Fe-species (major fraction of the Mössbauer spectra), Fe atoms are situated at a cubic environment and it can be attributed to the c-Fe 20 Rh 80 alloy based on their hyperfine parameters. In the second spe- cies, Fe atoms are placed in a non-local symmetry, which can be related to Fe atoms at the grain bound- aries or/and Fe small clusters. These Fe-clusters are in superparamagnetic state at room temperature, but they may be ordered below 45 K, as suggested by magnetization data. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Electrochemical techniques, in particular galvanic displacement and electrodeposition, are widely applied to prepare materials, such as: high purity metals [1–3], metallic alloys [4–6], ceramics [7–9] and semiconductors [10]. The main difference between these two methods is the application of external power sources. External voltage (or current flow) is an important parameter used to mate- rial fabrications in electrodeposition, while in galvanic displace- ment (also called immersion plating or cementation) it is eliminated once spontaneous electrochemical reactions take place between the electrolyte and substrate. However, the use of the gal- vanic displacement technique has been limited; it has been mostly applied to deposit few elements and some alloys [11–13]. Fe–Rh alloys have been an attractive material for researchers since the pioneer work of Fallot [14] that reported the first-order antiferromagnetic (AF) ? ferromagnetic (FM) phase transition for near equiatomic compositions. Such transition is observed only in a very narrow concentration range of 5% around x = 0.50 in the Fe 1x Rh x phase diagram [15–17] and happens close to room tem- perature. Furthermore, the AF–FM transition is strongly influenced by different parameters such as pressure, applied magnetic field, composition, and temperature. Recent studies have demonstrated that this transition is also accompanied by a volume increase of about 1–2% [18], a resistivity reduction [19,20] and a large change in entropy [21]. In light of these peculiar properties, Fe–Rh alloys have many potential applications such as heat assisted magnetic recording medium [18], MEMS (Microelectromechanical systems) devices [22], spin valve based devices and highly sensitive mag- netic sensors [23]. Thus, due to their potentials for technological applications, in the last eight decades Fe–Rh alloys have been extensively produced and studied, in a broad composition range by several methods, including sputtering [24,25], molecular beam epitaxy [26], induction melting [27,28], chemical synthesis [29]. Nevertheless, the electrodeposition of Fe–Rh alloys is hitherto still missing. In this work, we report the use of conventional electro- chemical techniques to prepare Rh-rich (80 at.%) Fe–Rh films either in crystalline or in nanocrystalline-like state. In particular, we pro- pose, for the first time, the electrodeposition of crystalline Fe–Rh films from a glycine-containing bath. Glycine electrolytes are par- ticularly attractive because are nontoxic and cost-effective. More- over, glycine has high buffering properties, which are important in the pH stabilization on the electrode surface during electrode- position [30]. The prepared Fe–Rh films were physically character- ized by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffractrometry (XRD) and Mössbauer 0925-8388/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2013.03.282 ⇑ Corresponding author. Tel.: +55 16 33019782; fax: +55 16 33222308. E-mail address: rodrnoce@iq.unesp.br (R.D. Noce). Journal of Alloys and Compounds 573 (2013) 37–42 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom