Electron paramagnetic resonance study of the ferroelectromagnet Pb(Fe 1/2 Nb 1/2 )O 3 through ferro-paraelectric transition G. Alvarez a, ⁎ , R. Font b , J. Portelles b , R. Valenzuela a a Departamento de Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, Coyoacan, DF, 04510 México b Departamento de Física Aplicada, Facultad de Física, Universidad de la Habana, San Lázaro y L. Vedado, La Habana, Cuba Received 14 February 2007; accepted 27 September 2007 Available online 2 October 2007 Abstract An electron paramagnetic resonance (EPR) study of ferroelectromagnet Pb(Fe 1/2 Nb 1/2 )O 3 (PFN) powders is presented. The EPR spectra show a single broad line in the 300–500 K temperature range, attributable to Fe 3+ ions. The onset of the ferro-paraelectric transition was determined from the temperature dependence of three main parameters deduced from the EPR spectra: g-factor, peak-to-peak linewidth and integrated intensity. These parameters indicate a behavior in agreement with a diffuse phase transition. © 2007 Elsevier B.V. All rights reserved. Keywords: Perovskites; Ferroelectrics; Electron paramagnetic resonance; Diffuse phase transitions 1. Introduction Lead iron niobate Pb(Fe 1/2 Nb 1/2 )O 3 (PFN) was discovered by Smolenskii in 1958 [1]; it is a ferroelectric material with perovskite structure (ABO 3 ). It is currently of interest as a component in commercial electroceramic materials due to their high dielectric constant and low sintering temperatures. At room temperature, the PFN is ferroelectric with Pb +2 in A site and Nb +5 in B site favoring the electric order. Its spontaneous polarization associated with ferroelectricity is caused by lattice distortion. The Fe +3 located in octahedral B sites provide the magnetic moment of the magnetic order. These are the basis of coexistence for ferroelectric–ferromagnetic orders in this ferroelectromagnet material. The phase transition from ferroelectric phase with rhombo- hedral structure to paraelectric phase with cubic structure was observed for this material at temperatures close to 380 K [1–3]. At temperatures below 145 K, this system shows an antiferromagnetic order [2–4]. Previous evidence of coupling between the ferroelectric and magnetic orders has been reported [3–5]. This coupling can result in the so-called magnetoelectric effect, where the magnetic properties of the ferroelectromagnet may be altered by the onset of the electric transition or by the application of an electric field. In general, for ferroelectromagnet materials, the change in electrical ordering caused by the ferro-paraelectric phase transition or by an external electric field produces a redistribu- tion of the electron spins; this leads to a change in the magnetic moments, and therefore a variation in magnetic properties [4]. Electron paramagnetic resonance (EPR) is the most powerful spectroscopic method available for obtaining local structural information and symmetry of paramagnetic ions incorporated in the structure [6]. This technique allows the investigation of the nature of magnetic phases in materials at different temperatures [7,8]. To our knowledge, however, studies of PFN material with EPR technique are scarce. Recently, we published a preliminary EPR study of PFN at low temperature [8], where a weak ferromagnetic signal (WFS) is observed. This WFS is attributed to canting of Fe +3 ion sublattices in the antiferromagnetic matrix, and is associated with the magnetoelectric effect. Available online at www.sciencedirect.com Materials Letters 62 (2008) 1737 – 1739 www.elsevier.com/locate/matlet ⁎ Corresponding author. Departamento de Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Av. Universidad S/N, Cd. Universitaria, Col. Copilco el Alto, Del. Coyoacan, C.P. 04510, México DF. Tel.: +52 55 5622 4653. E-mail address: memodin@yahoo.com (G. Alvarez). 0167-577X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2007.09.070