With the purpose of fabricating ceramics where ferroelectric and magnetic order coexist, ceramics of Pb͑Fe 1/2 Nb 1/2 ͒O 3 have been prepared using the traditional ceramic method following three different routes. The first is a direct via starting from oxide reagents and the other two use different kinds of FeNbO 4 precursors with either monoclinic or orthorhombic structures. Crystallographic and surface morphological studies were carried out by the powder x-ray diffraction and scanning microscopy techniques. The presence of Fe 2+ , detrimental to the ferroelectric and magnetic performance, was evaluated by x-ray photoelectron spectroscopy. The samples showed no structural differences, uniformly distributed grains, a ferro-paraelectric transition temperature at 110°C and a normal diffuse phase transition ͑nonrelaxor behavior͒. Differences in the degree of diffuseness, densities and grain size were observed depending on the kind of precursor. Measurements of dc and ac electrical resistivity, dielectric constant and dielectric loss were made as functions of temperature from room temperature to 250°C, at different frequency values ͑between 20 Hz and 1 MHz͒. Four conduction mechanisms were identified: hopping charge corresponding to low temperatures, small polarons and oxygen vacancies conduction at intermediate temperatures, and intrinsic ionic conduction at high temperatures. The best set of values of dielectric loss and dielectric constant, from the ferroelectricity point of view, were obtained when the precursor with orthorhombic structure was employed.
The dielectric behavior of ferroelectromagnetic Pb(Fe1∕2Nb1∕2)O3 ceramics obtained using the traditional ceramic method employing three different precursors was investigated by impedance spectroscopy in the temperature range of 200–300°C. This study was carried out by means of the simultaneous analysis of the complex impedance Z̃, electric modulus M̃, and admittance Ỹ functions from the measurements in the frequency range of 20Hz–1MHz. In correspondence to a previous structural, morphological, and temperature response study, appropriate microstructural and equivalent circuit models were established. Based on the brick layer model, three series of interconnected electrically distinct regions are considered: a conductive grain boundary layer, a capacitive grain boundary surface layer, and a resistive-ferroelectric bulk layer. Two conduction mechanisms were identified: a dielectric relaxation process due to localized conduction associated with the presence of oxygen vacancies and the nonlocalized conduction corresponding to long range conductivity associated with extrinsic mechanisms due, fundamentally, to Fe2+ presence. Both mechanisms were discerned to occur inside the grains and where the contributions of the grain boundary are neglected. Three conductivity components were deconvoluted: a longe range dc conductivity at the low frequency region, a capacitive behavior at higher frequencies, and a universal power law behavior in an intermediate-frequency region. Values of the activation energy corresponding to relaxation processes and dc conductivity were determined and excellent correlation with those obtained from the temperature response was found. A comparative analysis between the behaviors of each sample is presented.
Dielectric relaxation processes occurring near the ferroelectric-paraelectric phase transition of ferroelectromagnetic Pb(Fe1∕2Nb1∕2)O3 ceramics obtained by different precursors are discussed using microstructural and equivalent circuit modeling and the impedance spectroscopy technique. The frequency-temperature response was obtained from room temperature to 300°C and from 20Hzto1Mz. In correspondence with a previous structural, morphological, and temperature response study, appropriate microstructural, and equivalent circuit models were established. The frequency response study was carried out by means of the simultaneous analysis of the complex dielectric constant ε̃ and admittance Ỹ functions and the dielectric loss, tanδ. A strong absorption near the transition temperature region at a frequency around 1MHz is discussed and is attributed with relaxation processes associated with domain reorientation, domain wall (DW) motion, and the dipolar behavior of ferroelectric materials. Such processes were found to take place inside the grain, and their low characteristic frequencies are explained by clamping effects of the DW due to the thermally activated diffusion of oxygen vacancies. At frequencies before relaxation, the high polarization values are due to small polaron mechanisms associated with the presence of Fe2+. The relaxation processes are very much conditioned by the grain and domain sizes, the degree of deformation of the lattice and the crystallites, as well as the potential barriers in the grain boundaries. Values of the activation energy corresponding to the different relaxation processes were determined from fitting of experimental data, identifying thus the involved mechanisms, and an excellent agreement with those obtained from the temperature response [Raymond et al., J. Appl. Phys. 97, 084107 (2005)] was found. The relaxation processes studied here are an evidence of domain structure.
Electrical detection of nonlinear ferromagnetic resonance in single elliptical permalloy thin film using a magnetic tunnel junction Appl. Phys. Lett. 99, 232506 (2011) Loss of magnetization induced by doping in CeO2 films J. Appl. Phys. 110, 113902 (2011) Giant magnetoelectric torque effect and multicoupling in two phases ferromagnetic/piezoelectric system J. Appl. Phys. 110, 104510 (2011) Magnetic properties of L10-FePt/permalloy exchange-spring films J. Appl. Phys. 110, 103911 (2011) The origin of athermal training in polycrystalline metallic exchange bias thin films Appl. Phys. Lett. 99, 222508 (2011) Additional information on J. Appl. Phys. In this study, (011)-highly oriented Sr, Nb co-doped BiFeO 3 (BFO) thin films were successfully grown on SrRuO 3 /Si substrates by rf-magnetron sputtering. The presence of parasite magnetic phases was ruled out based on the high resolution x-ray diffraction data. BFO films exhibited a columnar-like grain growth with rms surface roughness values of %5.3 nm and average grain sizes of %65-70 nm for samples with different thicknesses. Remanent polarization values (2P r ) of 54 lC cm À2 at room temperature were found for the BFO films with a ferroelectric behavior characteristic of an asymmetric device structure. Analysis of the leakage mechanisms for this structure in negative bias suggests Schottky injection and a dominant Poole-Frenkel trap-limited conduction at room temperature. Oxygen vacancies and Fe 3þ /Fe 2þ trap centers are consistent with the surface chemical bonding states analysis from x-ray photoelectron spectroscopy data. The (011)-BFO/ SrRuO 3 /Si film structure exhibits a strong magnetic interaction at the interface between the multiferroic film and the substrate layer where an enhanced ferromagnetic response at 5 K was observed. Zero-field cooled (ZFC) and field cooled (FC) magnetization curves of this film system revealed a possible spin glass behavior at spin freezing temperatures below 30 K depending on the BFO film thickness.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.