Structure, Thermal and Magnetic Properties of Nanocrystalline Materials

Dear Colleagues,

Nanocrystalline (NC) materials have attracted great attention during the last decades owing to their superior physical, mechanical, magnetic, and electrochemical properties compared to their coarse-grained counterparts due to their small crystallite size and the presence of a large amount of atoms residing in grain boundaries and interfaces. Since the volume fraction of interfaces can reach as much as 50% for 5 nm grains, surfaces and interfaces play a crucial role in controlling the process kinetics at the nanoscale level in many applications in the interdisciplinary fields of energy storage, sensors, drug delivery, functionalization of nanostructures, electrochemistry, etc. NC materials can be prepared by different methods such as mechanical alloying (MA), rapid solidification, sol gel, hydrothermal, spray pyrolysis, electrodeposition, chemical vapour deposition (CVD), physical vapour deposition (PVD), inert gas condensation, spin coating, chemical bath deposition (CBD), etc. Besides, the applications of NC materials are strongly linked to the preparation conditions and methods which have an influence on their atomic arrangements and microscopic characteristics that affects not only the product’s overall attributes, but also their performance and future uses. Hence, to achieve high performance characterization, altering the structure of the materials has an impact on the material’s overall properties. Also, the modification of the morphological and microscopic characteristics of materials leads to noticeable changes in their properties and behaviours. Therefore, it is important to be able to control the structure, microstructure, thermal, mechanical, and magnetic properties of materials.   

This Special Issue deals with structural, microstructural, thermal stability, mechanical, and magnetic characterization of NC. Both reviews and original papers are welcomed for submission.

Prof. Dr. Safia Alleg
Prof. Dr. Joan-Josep Suñol
Guest Editors

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• Nanocrystalline materials;
• Powder alloys;
• Thin films;
• Ribbons alloys;
• Structure;
• Microstructure;
• Magnetic properties;
• Thermal behavior.

Title: Investigations on structural, Magnetic, and dielectric properties of the multiferroic Bi_0.8Er_0.1Ba_0.1Fe_0.96Cr_0.02Mn_0.02O₃ nanoparticles.

Authors: Benali, E.M. Benali, A. Bougoffa, M.A. Valente, M.P.F. Graça, B.F.O. Costa.

Abstract:

In the present work, efforts have been made to synthesize the Bi_0.8Er_0.1Ba_0.1Fe_0.96Cr_0.02Mn_0.02O₃ nanoparticles via Sol-gel route and were denoted as successful. The structural analysis confirms the distorted rhombohedral structure (the R3C space group) along with some impurities (Bi₄O₇ and Ba₂FeO₄). Nanosize criteria of the synthesized material was confirmed through Williamson-Hall formalism and TEM analyses. The alterations in the vibration modes observed in Raman spectra (expansion, reduced intensity, merge, and shift) strongly confirmed the substitution effect on structure. Investigation of magnetic properties reveals that the BEBFCM sample possess high magnetic saturation which was assigned to the Ferromagnetic interactions as result of substitutions. Mössbauer spectroscopy revealed two Fe cations differently coordinated confirming that magnetization results from a coexistence of Ferromagnetic and Antiferromagnetic contributions. Further, the BEBFCM nanoparticles were found to exhibit an important value of maximum energy product (BH)_max, which makes them good candidate for permanent magnet applications. Additionally, the BEBFCM sample with giant dielectric constant and low dielectric loss tangent could be an effective candidate for capacitors and dynamic random-access memory applications.

Keywords: multiferroics; magnetism; Mössbauer spectroscopy, dielectric relaxation.