About: Ferrimagnetism is a(n) research topic. Over the lifetime, 7609 publication(s) have been published within this topic receiving 151259 citation(s).
01 Sep 1955
B. A. Calhoun1•Institutions (1)
Abstract: 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.
F.K. Lotgering1•Institutions (1)
Abstract: A new method is described for the preparation of polycrystalline materials with oriented crystals by reaction of the oriented grains of a strongly anisotropic ferrimagnetic with non-oriented grains of usually non-magnetic components. Using this type of reaction, for which the name “topotactical (or “topotaxial”) reaction” is proposed, oriented samples of Ba3CoδZn2−δFe24O41, BaCoδZn2−δFe16O27, Ba2Zn2Fe12O22 and BaCoδTiδFe12−2δO19, which have related hexagonal crystal structures, have been prepared as well as some ferrites having the cubic spinel structures.
•01 Jan 1997
Abstract: 1. Magnetostatic phenomena 2. Magnetic measurements 3. Atomic magnetic moments 4. Macroscopic experimental techniques 5. Magnetic disorder 6. Ferromagnetism 7. Antiferromagnetism and ferrimagnetism 8. Magnetism of metals and alloys 9. Magnetism of ferromagnetic oxides 10. Magnetism of compounds 11. Magnetism of amorphous materials 12. Magnetocrystalline anisotrophy 13. Induced magnetic anisotropy 14. Magnetostriction 15. Observation of domain structures 16. Spin distribution and domain walls 17. Magnetic domain structure 18. Technical magnetization 19. Spin phase transition 20. Dynamic magnetization 21. Various phenomena association with magnetization 22. Engineering applications of magnetic materials
TL;DR: The magnetization in the ferrimagnetic region below 16 kelvin was substantially increased after illumination and could be restored almost to its original level by thermal treatment and these effects are thought to be caused by an internal photochemical redox reaction.
Abstract: Photoinduced magnetization was observed in a Prussian blue analog, K0.2Co1.4- [Fe(CN)6]·6.9H2O. An increase in the critical temperature from 16 to 19 kelvin was observed as a result of red light illumination. Moreover, the magnetization in the ferrimagnetic region below 16 kelvin was substantially increased after illumination and could be restored almost to its original level by thermal treatment. These effects are thought to be caused by an internal photochemical redox reaction. Furthermore, blue light illumination could be used to partly remove the enhancement of the magnetization. Such control over magnetic properties by optical stimuli may have application in magneto-optical devices.
Robert C. Pullar1•Institutions (1)
Abstract: Since their discovery in the 1950s there has been an increasing degree of interest in the hexagonal ferrites, also know as hexaferrites, which is still growing exponentially today. These have become massively important materials commercially and technologically, accounting for the bulk of the total magnetic materials manufactured globally, and they have a multitude of uses and applications. As well as their use as permanent magnets, common applications are as magnetic recording and data storage materials, and as components in electrical devices, particularly those operating at microwave/GHz frequencies. The important members of the hexaferrite family are shown below, where Me = a small 2+ ion such as cobalt, nickel or zinc, and Ba can be substituted by Sr: • M-type ferrites, such as BaFe12O19 (BaM or barium ferrite), SrFe12O19 (SrM or strontium ferrite), and cobalt–titanium substituted M ferrite, Sr- or BaFe12−2xCoxTixO19 (CoTiM). • Z-type ferrites (Ba3Me2Fe24O41) such as Ba3Co2Fe24O41, or Co2Z. • Y-type ferrites (Ba2Me2Fe12O22), such as Ba2Co2Fe12O22, or Co2Y. • W-type ferrites (BaMe2Fe16O27), such as BaCo2Fe16O27, or Co2W. • X-type ferrites (Ba2Me2Fe28O46), such as Ba2Co2Fe28O46, or Co2X. • U-type ferrites (Ba4Me2Fe36O60), such as Ba4Co2Fe36O60, or Co2U . The best known hexagonal ferrites are those containing barium and cobalt as divalent cations, but many variations of these and hexaferrites containing other cations (substituted or doped) will also be discussed, especially M, W, Z and Y ferrites containing strontium, zinc, nickel and magnesium. The hexagonal ferrites are all ferrimagnetic materials, and their magnetic properties are intrinsically linked to their crystalline structures. They all have a magnetocrystalline anisotropy (MCA), that is the induced magnetisation has a preferred orientation within the crystal structure. They can be divided into two main groups: those with an easy axis of magnetisation, the uniaxial hexaferrites, and those with an easy plane (or cone) of magnetisation, known as the ferroxplana or hexaplana ferrites. The structure, synthesis, solid state chemistry and magnetic properties of the ferrites shall be discussed here. This review will focus on the synthesis and properties of bulk ceramic ferrites. This is because the depth of research into thin film hexaferrites is enough for a review of its own. There has been an explosion of interest in hexaferrites in the last decade for more exotic applications. This is particularly true as electronic components for mobile and wireless communications at microwave/GHz frequencies, electromagnetic wave absorbers for EMC, RAM and stealth technologies (especially the X and U ferrites), and as composite materials. There is also a clear recent interest in nanotechnology, the development of nanofibres and fibre orientation and alignment effects in hexaferrite fibres, and composites with carbon nanotubes (CNT). One of the most exciting developments has been the discovery of single phase magnetoelectric/multiferroic hexaferrites, firstly Ba2Mg2Fe12O22 Y ferrite at cryogenic temperatures, and now Sr3Co2Fe24O41 Z ferrite at room temperature. Several M, Y, Z and U ferrites have now been characterised as room temperature multiferroics, and are discussed here. Current developments in all these key areas will be discussed in detail in Sections 7 The microwave properties of hexagonal ferrites , 8 Magnetoelectric (ME), multiferroic (MF) and dielectric properties of hexaferrites , 9 Hexaferrite composites , 10 Hexagonal ferrite fibres , 11 Nanoscale hexagonal ferrite particles, ceramics and powders of this review, and for this reason now is the appropriate time for a fresh and critical appraisal of the synthesis, properties and applications of hexagonal ferrites.