Magnetic and Structural Behaviour of Cobalt & Nickel Substituted Calcium W-Type Nanosize Hexaferrites

The available literature and research work on W-type hexaferrites is mainly focused on Co- and Zn-based calcium W-type hexagonal ferrites with a variety of cationic substitutions. The Modifications in the properties of the Calcium W-type ferrite based on Ni2+ as the divalent metal ion, however, is not studied sufficiently in the research literature vailable. In this study, the focus is mainly on the effects of substitution of Ni2+ on the properties of CaCo2W exaferrites. The investigations carried out are mainly XRD, SEM and VSM. The main objective of this research investigation is to study the effect of substitution of Nickel and Cobalt on the structural and magnetic properties of calcium W-type hexaferrite CaCo2-xNixFe16O27 (x=0, 1 and 2). XRD analysis and characterization revealed slight decrease in the values of lattice constants ‘a’ and ‘c’ with increase in concentration ‘x’. The particle size was confirmed from SEM and TEM images. The analysis of VSM for magnetic properties reveals decrease in coercivity and increase in the values of saturation magnetization as concentration increases. The results of measurements made bythe various experimental techniques and the observations were compared to understand the crystalline and magnetic structure of the compounds

Ferrite

Ferrites are highly interesting high-tech materials. The book covers their classification, structure, synthesis, properties and applications. Emphasis is placed an biomedical applications, degradation of organic pollutants, high frequency applications, photocatalytic applications for wastewater remediation, solar cell applications, removal of organic dyes and drugs from aquatic systems, and the synthesis of hexagonal ferrites.

Hexagonal Ferrites, Synthesis, Properties and Their Applications

We intend to report on possible fabrication routes for all types of hexagonal ferrites which are known for their wide area of use and applications. Hexagonal ferrites have now become an intense topic of research as they are the part of most of magnetic recording and data storage applications globally. Hexagonal or popularly known as ‘Heaxa-ferrites’ are known for their utilization in permanent magnets and their utilization in electrical devices being operated at high frequencies especially at GHz frequencies. We have presented in this chapter all main six types of hexagonal ferrites i.e. M Type, Z-Type, Y-type, W-type, X-Type and U-type hexa-ferrites. Hexaferrites belong to ferromagnetic class of magnetic materials and their properties are purely dependent on intrinsic structure of ferrites. In this chapter, we aim to discuss more on M-type of hexa-ferrites, their properties and their applications. Also, recent advances on M-type ferrites are also a part of this chapter.

Application of Spinel and Hexagonal Ferrites in Heterogeneous Photocatalysis

Semiconducting materials display unique features that enable their use in a variety of applications, including self-cleaning surfaces, water purification systems, hydrogen generation, solar energy conversion, etc. However, one of the major issues is separation of the used materials from the process suspension. Therefore, chemical compounds with magnetic properties have been proposed as crucial components of photocatalytic composites, facilitating separation and recovery of photocatalysts under magnetic field conditions. This review paper presents the current state of knowledge on the application of spinel and hexagonal ferrites in heterogeneous photocatalysis. The first part focuses on the characterization of magnetic (nano)particles. The next section presents the literature findings on the single-phase magnetic photocatalyst. Finally, the current state of scientific knowledge on the wide variety of magnetic-photocatalytic composites is presented. A key aim of this review is to indicate that spinel and hexagonal ferrites are considered as an important element of heterogeneous photocatalytic systems and are responsible for the effective recycling of the photocatalytic materials.

Strain-Mediated Magneto-Electric Effects in Coaxial Nanofibers of Y/W-Type Hexagonal Ferrites and Ferroelectrics

Nanofibers of Y- or W-type hexagonal ferrites and core–shell fibers of hexagonal ferrites and ferroelectric lead zirconate titanate (PZT) or barium titanate (BTO) were synthesized by electrospinning. The fibers were found to be free of impurity phases, and the core–shell structure was confirmed by electron and scanning probe microscopy. The values of magnetization of pure hexagonal ferrite fibers compared well with bulk ferrite values. The coaxial fibers showed good ferroelectric polarization, with a maximum value of 0.85 μC/cm2 and 2.44 μC/cm2 for fibers with BTO core–Co2W shell and PZT core–Ni2Y shell structures, respectively. The magnetization, however, was much smaller than that for bulk hexaferrites. Magneto-electric (ME) coupling strength was characterized by measuring the ME voltage coefficient (MEVC) for magnetic field-assembled films of coaxial fibers. Among the fibers with Y-type, films with Zn2Y showed a higher MEVC than films with Ni2Y, and fibers with Co2W had a higher MEVC than that of those with Zn2W. The highest MEVC of 20.3 mV/cm Oe was measured for Co2W–PZT fibers. A very large ME response was measured in all of the films, even in the absence of an external magnetic bias field. The fibers studied here have the potential for use in magnetic sensors and high-frequency device applications.