In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Hexagonal ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics

As compared to bulk materials, magnetic nanoparticles possess distinct magnetic properties and attempts have been made to exploit their beneficial properties for technical and biomedical applications, e.g. for magnetic fluids, high-density magnetic recording, or biomedical diagnosis and therapy. Early magnetic fluids (MFs) were produced by grinding magnetite with heptane or long chain hydrocarbon and a grinding agent, e.g. oleic acid [152]. Later procedures for MFs precipitated Fe 3+/Fe 2+ of an aqueous solution with a base, coated the particles by oleic acid, and dispersed them in carrier liquid [161]. However, besides the elemental composition and crystal structure of the applied magnetic particles, particle size and particle size distribution determine the properties of the resulting MF. Many methods for nanoparticle synthesis including the preparation of metallic magnetic particles have been described in the literature. However, there still remain important questions, e.g. concerning control of particle size, shape, and monodispersity as well as their stability towards oxidation. Moreover, peptization by suitable surfactants or polymers into stable MFs is an important issue since each application in engineering or biomedicine needs special MFs with properties adjusted to the requirements of the system.

Synthesis and Characterization

Magnetocaloric effect: From materials research to refrigeration devices

Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

Raman Spectra and Vibrational Analysis of BaFe12O19Hexagonal Ferrite

An investigation of the magnetic anisotropy change in BaFe12−2xTixCoxO19 single crystals

Structure, magnetic and electrical behaviour of La0.7Sr0.3Mn1−xTixO3 with 0⩽x⩽0.3

This paper reports the first single-crystal Raman spectra of substituted barium hexaferrites, BaFe12−2x MexCoxO19 (Me=Ir, Ti). The spectra were investigated in the 200–900 cm−1 range and are discussed in comparison with unsubstituted barium hexaferrite. Emphasis was placed on the different factors influencing the Raman spectra of substituted barium hexaferrites, namely the mass of the substituting cation, the ionic radius and charge and the ordering on the five distinct iron sites. Copyright © 1999 John Wiley & Sons, Ltd.

H. Vincent

Papers

Raman Spectra and Vibrational Analysis of BaFe12O19Hexagonal Ferrite

An investigation of the magnetic anisotropy change in BaFe12−2xTixCoxO19 single crystals

Structure, magnetic and electrical behaviour of La0.7Sr0.3Mn1−xTixO3 with 0⩽x⩽0.3

Raman study of substituted barium ferrite single crystals, bafe12-2xmexcoxo19 (me = ir, ti)

Structure cristalline d'un conducteur métallique bidimensionnel: Le bronze violet de potassium et molybdene K0.9Mo6O17